Status: Spanish runners-up Nicknames: Barca, BlaugranaTHE LEGEND: Barcelona took time to establish themselves as a true force in Europe's elite competition, but they have made up for lost time in recent seasons, claiming Champions League glory in 2006, 2009 and 2011.
Prior to those recent triumphs, Barca's 1992 maiden coronation as European champions was all they had to show for their efforts in this competition, with the record-breaking success of domestic rivals Real Madrid heightening their desire to take strides up the list of winners.
Barca also won the Cup Winners' Cup four times (1978-79, 1981-82, 1988-89, 1996-97) and the Fairs Cup on three occasions (1955-56, 1958-60, 1965-66). The Catalan giants have won UEFA's European Super Cup four times.
CALLING THE SHOTS: Tito Vilanova
Replacing the legendary Pep Guardiola would have been an almost impossible task for a Camp Nou "outsider," so the club wisely turned to his longtime assistant to continue the work that has seen Barca establish themselves as the kings of European football over the last decade.
Vilanova is not a man to seek out attention or create shockwaves, so it has been no surprise to see him adopt a policy of evolution rather than revolution since becoming top man.
The fluid playing style this club are famous for will not be altered and, after many observers have suggested Vilanova is the tactical mastermind behind Guaridola's historic reign as Barca boss, the second-in-command now gets his chance to confirm he can be the main man.
Vilanova enjoyed a modest playing career and has joined the ranks of modern coaches who are succeeding on the touchline without a celebrated record on the pitch.
THE GAME PLAN: There is no great secret to Barcelona's brilliance as the simplicity of their approach makes them special. Having assembled a squad of players that has been hailed as the greatest of all time, Guardiola and Vilanova have merely provided a framework for the magic to flow, and the stream of fantasy produced by Barca has been relentless.
The masterful Lionel Messi is the heartbeat of this team with his goals and incisive passing, but there is a threat exploding from every facet of the team, including the star names waiting for their chance on the bench. Experienced professionals Cesc Fabregas, Javier Mascherano and new boy Alex Song may be among those waiting for their first-team chances this season.
Their 4-3-3 formation could be diluted to a 4-2-3-1 for some Champions League games this season, as negative tactics from opponents have proved to be relatively successful against Barca over the last couple of years.
BIG HITTER: Lionel Messi
The biggest of the big hitters in world football, Messi's consistent brilliance has made him an irresistible force as Barcelona have established themselves as the kings of club football.
After bagging a truly astonishing 72 goals for club and country last season, this 25-year-old genius must have wondered how he finished the season without another La Liga or Champions League medal to add to his collection, yet that disappointment will merely fuel his desire for more.
Apparently tireless and immune to serious injury despite the heavy-handed treatment handed him by fearful opponents, Messi will eventually claim his place in the history books as one of the game's true legends.
CAPTAIN FANTASTIC: Carles Puyol
After missing out on Euro 2012 through injury, 34-year-old Puyol had a full summer to reflect on what might have been for Barcelona last season, and the shaggy-haired centre back is convinced the good times will roll once again under new boss Vilanova.
"Tito knows our team like nobody else, he knows its philosophy through and through, and was always the perfect choice to take over," the three-time Champions League-winning skipper said. "Pep leaving was obviously sad for all of us, but Tito taking over softens the blow."
NEW KID ON THE BLOCK: Jordi Alba
Improving this brilliant Barcelona team is no easy task, but the capture of this brilliantly efficient full back should have done just that.
Signed from Valencia in a £14 million deal, Alba instantly solves the weak spot on the left side of the Barca defence and arrives with a record that suggests he should be a risk-free signing. He was part of Spain's Euro 2012-winning squad.
SHOOTING STAR: Cristian Tello
Barcelona chiefs were reported to be eager to offload this 21-year-old Spanish attacking starlet as they believed he would struggle to force his way in the Barcelona first team, yet boss Vilanova made it clear that he wanted to retain Tello, and he looks set to hand him plenty of first-team chances in the coming months.
Liverpool were among the clubs linked ahead of the new season, but Vilanova is clear in his admiration for his talents. "Tello has never been on any list of players we wanted to move on," he insists. "For us, it has always been clear he would stay with the first team. He can be important for us this season."
SECRET WEAPON: David Villa
The return from injury of the brilliant Villa to the Barcelona lineup offers the potential to give them even more attacking potency as, while this Spain great has not always been at his best since moving to the Camp Nou from Valencia in 2010, his finishing touch could be vital to finish off Barca's sublime buildup play.
A broken leg sustained at the World Club Championship in December forced him to miss the second half of last season and Euro 2012, but he has returned in good time for this campaign and will be eager to win the Champions League again after he scored in the 2011 final against Manchester United at Wembley.
THE WEAK SPOT: When so much emphasis is on attacking football, defending is often overlooked and Barcelona's weakness when defending set-pieces is an area Vilanova needs to address. Opponents have enjoyed too much success with well-directed balls into the box, and it is a long-standing concern.
What happens if Messi gets injured? It is a question that has been asked time and again in recent years, but Barcelona have been fortunate that there has not been a need for them to answer it yet. So much of their success stems from one brilliant player, and that is a perilous position to be in.
Finally, we have yet to find out how Vilanova will react when the pressure is applied at the business end of a season. He has always had the comfort of standing behind Guardiola on nights of high tension and drama, but the buck stops with him now.
VERDICT: Opponents may have found a way to muzzle Barcelona to a degree, but they remain a thrilling force and are worthy favourites to reclaim the Champions League crown.
Status: Portuguese runners-up Nicknames:Aguias (Eagles), Encarnados (Reds)
THE LEGEND: The Lisbon Eagles are long-standing continental protagonists, having claimed the European Cup on two memorable occasions in 1960 and 1961 -- upsetting the odds in beating Barcelona and Real Madrid in those finals -- and coming runners-up in the same competition five times (1963, 1965, 1968, 1988 and 1990). Another near-miss took place in 1983 when they were defeated by Anderlecht in the final of the UEFA Cup.
The Champions League has proved a harder nut for them to crack and they have been unable to do better than a couple of quarterfinal appearances in 2005-06 and last season, when they went out to eventual winners Chelsea.
CALLING THE SHOTS: Jorge Jesus
This authoritarian, attack-conscious and stubborn 58-year-old boss is not especially known for his modesty. His installation in the Benfica hot seat in the summer of 2009 was the first big appointment of his coaching career and he responded well to the challenge, immediately leading the Lisbon giants to the national championship.
A former midfielder with Sporting Lisbon, Estrela Amadora and Farense, Jesus has certainly gone around the Portuguese football block, notably steering the likes of Estrela Amadora, Felgueiras and Vitoria Setubal to top-flight promotions and also working at Guimares, Uniao Leiria, Belenenses and Braga, whom he guided to a fine fifth-place domestic league finish and the last 16 of the 2008-09 UEFA Cup.
THE GAME PLAN: Although Jorge Jesus does, on occasion, go with two strikers -- normally using Oscar Cardozo as the target man with Rodrigo playing off him -- the Benfica coach has enjoyed much more success with an adventurous 4-2-3-1 with Cardozo or new signing Lima as the lone frontman backed up by a highly technical attacking midfield triumvirate of Salvio/Ola John on the right, Enzo Perez/Nolito on the left and Argentina star Pablo Aimar through the middle.
Jesus also likes one of the two nominal holding midfielders (probably Carlos Martins) to frequently break into advanced areas and, in alliance with Aimar, set up the one-twos and killer through-balls. An important offensive route for Benfica is provided by right back Maxi Pereira, whose regular sorties into the opposition half usually involve him cutting inside.
Indeed, both Benfica full backs push on and, when they do, the one genuine enforcer -- Nemanja Matic -- drops back, thus creating a 3-3-3-1. Jesus works very hard on the team's set-pieces and it regularly reaps rewards.
BIG HITTER: Pablo Aimar
This 32-year-old Argentine attacking midfielder has lost some pace and can be inconsistent, but he can still make a huge difference with his exquisite passing and dribbling on his day.
While some suggest he has not quite fulfilled the promised he showed in his early years at leading Argentine club River Plate, he has had his share of the prizes: a world title with his country's Under-20s in 1997, two Liga crowns with Valencia (2002 and 2004) and a UEFA Cup triumph with the same club in 2004. In the 2000-01 season, Aimar was part of the Valencia side that lost the Champions League final to Bayern Munich on penalties.
CAPTAIN FANTASTIC: Luisao
A composed, resolute and physically imposing Brazilian centre back, Luisao joined the club in 2003 from top Belo Horizonte outfit Cruzeiro and was appointed skipper three years later. Benfica got themselves a bargain when they picked him up, paying just £900,000. He was a key figure in the club's league titles in 2005 and 2010 and has been a symbol of the club over the last decade.
A full Brazil international since 2001, Luisao has 43 caps to date and helped his country win the Copa America in 2004. Strangely, he has often expressed a wish to try his luck in another championship but to date nothing has materialised.
NEW KID ON THE BLOCK: Lima
Just a few days after helping Braga qualify for the group stages of the Champions League, the Brazilian striker promptly moved on, completing a surprising switch to Benfica as the transfer window clock ticked down.
The top scorer in the Portuguese League last term with 20 goals, Lima served Braga splendidly for two years, leading the line for them as they finished runners-up to FC Porto in the 2010-11 Europa League.
Prior to crossing the Atlantic in 2009 to play for Portuguese provincials Belenenses, he had been pigeon-holed in Brazilian football circles as a journeyman frontman, someone with little or no prospect of making it big in Europe.
SHOOTING STAR: Rodrigo
A speedy, elusive and sharp front-runner, Rodrigo was born in Rio but raised in Spain and now is a naturalised Iberian. After featuring in the youth ranks of Celta Vigo and Real Madrid, he moved in the summer of 2010 to Benfica, who instantly farmed him out for a stint in the Premier League with Bolton.
A star of the Spain Under-19 and Under-21 sides, this 21-year-old returned to Lisbon at the start of last season and has not stopped catching the eye since.
SECRET WEAPON: Ola John
This highly promising Dutch winger was signed for £8.1 million this summer from FC Twente and he comes with a big reputation. A two-footed winger of considerable dash and guile, he earned his first call-up to the full Netherlands squad for the game against England at Wembley earlier this year.
Born in Liberia, he was just 2 years old when his father was killed in the country's civil war, forcing Ola, his mother and brothers to flee to the Netherlands. He is the younger brother of ex-Fulham frontman Collins John.
THE WEAK SPOT: Jorge Jesus' insistence on going forward at every opportunity comes with an obvious health warning. Benfica can commit too many to the attack, leaving themselves undermanned in the middle of the park and extremely vulnerable to a brisk counter. They can be exposed defensively on the flanks too, and Paraguayan left back Lorenzo Melgarejo is a weak link.
Also, they can struggle to dictate the tempo of a game, while the coach needs a crash course in rotating his personnel as last season he burnt out a number of his key men. Finally, the last-minute summer sales of star midfielders Axel Witsel and Javi Garcia means a late, late reshuffle.
VERDICT: A spot in the knockout phase is perfectly within their reach, but only if coach Jesus resists the temptation to live up to his billing as a tactical "tinkerman," as his meddling is often counterproductive.
Status: Russian runners-up Nicknames:Krasno-Belye (Red-and-Whites), Myaso (The Meat)
THE LEGEND: Without ever reaching a European final, Spartak have proved themselves doughty midweek warriors over the years, doing especially well in the 1990-91 European Cup when they knocked out both Real Madrid and Diego Maradona's Napoli before falling in the semifinals to Marseille.
In the same competition they qualified for the last eight in 1980-81 and 1995-96, and they also have appeared in the semis of the Cup Winners' Cup (1992-93) and UEFA Cup (1997-98).
One of their most painful moments was the 10-3 aggregate hammering they received from FC Porto in the quarterfinals of the 2010-11 Europa League.
CALLING THE SHOTS: Unai Emery
An outstanding young Spanish boss headhunted by Spartak in the offseason after four highly satisfying campaigns with Valencia. One of just three coaches to have reigned as long at Valencia, he could not have done a better job for the Mestalla outfit in the Spanish championship, steering them to excellent third-place finishes in each of the last three seasons.
The Champions League, however, has not proved a happy hunting ground for him, as he was unable to prevent his side being eliminated by Schalke in the round of 16 in the 2010-11 campaign and suffered elimination at the group stage last term.
He first made a name for himself as the coach of Almeria, guiding them to promotion to the top flight in 2006-07 and then overachieving by finishing in seventh place the following year.
THE GAME PLAN: A most methodical training ground instructor, Emery just loves to ring the tactical changes on a match day, one minute using his favoured 4-2-3-1, the next going with a 4-3-3 or 4-4-2.
His teams tend to be athletic, strong and speedy, with one key commandment being a high pressing game. Another mantra is his insistence on his side leaping straight out of the blocks to put the opposition under intense pressure for the first 15 to 20 minutes. Late winners are a speciality too.
Emery encourages Spartak to take risks. All his defensive midfielders -- Romulo, Demy De Zeeuw and Kim Kallstrom -- are comfortable on the ball; the full backs push on purposefully, particularly the left-sided Dmitri Kombarov; while Brazilian Ari, the central man in the attacking midfield trio, spends much of his time supporting line leader Emmanuel Emenike. The two other offensive midfielders have contrasting roles, with Irishman Aiden McGeady the classic right winger and Diniyar Bilyaletdinov more tucked in.
BIG HITTER: Emmanuel Emenike
This muscular, explosive Nigerian striker has proved an extremely valuable leader of the line since joining Spartak in a £9 million deal from Fenerbahce in July of last year. He was so effective in Turkish football with Karabukspor and Fenerbahce that attempts were made to naturalise him, though they came to nought.
He first came to prominence in South Africa with FC Cape Town and is often compared in style to the former Club Brugge, Everton and Nigeria attacker Daniel Amokachi.
CAPTAIN FANTASTIC: Andrey Dikan
This tall and highly experienced Ukraine international goalkeeper was handed the armband this summer when usual team leader Sergei Parshivlyuk was ruled out for six months with a seriously damaged knee. In only his second competitive game for Spartak in 2010, Dikan gave a man-of-the-match performance in a 1-0 victory away to Marseille in the 2010-11 Champions League.
Dikan would have been selected for Euro 2012 if had not been involved in a horrific collision with Zenit striker Aleksandr Kerzhakov last spring, an incident that left the former with head and facial injuries.
NEW KID ON THE BLOCK: Romulo
A young Brazilian defensive midfielder bought for £7.2 million from top Rio de Janeiro side Vasco da Gama, this youngster recently helped Brazil win a silver medal at the London Olympics. Diligent in his marking and his tracking back, a good passer of the ball and not at all fearful of pushing forward, he scored on his debut for Spartak. Romulo was once on the books of Group F opponents Benfica as a youth but had to be let go because of an administrative mix-up.
SHOOTING STAR: Artyom Dzyuba
A lanky Peter Crouch-esque central striker who plays with a great deal of flair and elegance in spite of his stature, and such are his strengths on the floor that he is sometimes used as a winger.
A graduate of the Spartak soccer school, he certainly knows where the goal is and has had his share of memorable European nights, especially when scoring twice in a 2-2 draw with Tottenham in a 2008-09 Europa League tie. Now 24, he was in Russia's preliminary squad for Euro 2012 but did not make the final 23.
SECRET WEAPON: Jano Ananidze
A baby-faced 19-year-old attacking midfielder from Georgia whose dazzling dribbling ability, superb free kicks and versatility -- he can play just behind the strikers or on either flank -- makes him the ideal impact player. Small and slightly built but terribly elusive all the same, Ananidze is a real talent in the making.
In the Spartak senior squad for the past three years, he became in 2009 the youngest-ever scorer in the history of the Russian league, netting against Lokomotiv Moscow at the age of just 17 years and eight days. Ananidze was schooled at the academies of Dinamo Tbilisi and Dynamo Kiev, joining Spartak in 2007.
THE WEAK SPOT: Their defence is by no means the strongest in this competition. In goal, Dikan can make silly mistakes, and the Argentine-Czech centre-back pairing of Nicolas Pareja and Marek Suchy is not exactly imperious.
Right back Yevgeni Makeev could be a liability as well. At times Spartak commit too many players to attack, leaving the back door unguarded. Generally they are not comfortable when pressed, often making unforced errors and against the very best in Europe, that pressure is certain to be applied incessantly.
VERDICT: Expect Unai Emery's European trek across the desert to continue, though they will fancy their chances of pushing for the second spot in Group G behind Barcelona.
Status: Scottish champions Nicknames: The Bhoys, the Hoops
THE LEGEND: They may have won a colossal 92 domestic trophies in their illustrious history, but Celtic's pride in becoming the first British club to lift the ultimate prize in European club football back in 1967 remains their most cherished achievement.
Their 2-1 victory against Inter Milan in the European Cup final 45 years ago is the stuff of legend, with manager Jock Stein and his team of "Lisbon Lions" immortalised forever.
Champions League success has been hard to come by for Celtic in recent years, but they enjoyed a memorable run in the 2003 UEFA Cup, only losing out to Jose Mourinho's FC Porto in the final.
CALLING THE SHOTS: Neil Lennon
Lennon hailed his achievement of guiding Celtic back into the group stages of the Champions League as "my finest in football," and with good reason.
After all, this 41-year-old novice coach has overcome huge obstacles to reach this grand stage, and not all of them have been football-related. As a Northern Irish Catholic thrust into the hotbed environment that is Glasgow football, Lennon has been forced to endure pressures few before him have faced and, while he has not always helped himself with some of his inflammatory public declarations, he has matured into a fine coach.
Having worked under Martin O'Neill's guidance at Leicester and Celtic, Lennon credits his compatriot with giving him the inspiration to move into management, and now he gets his chance to test himself against the continent's finest.
THE GAME PLAN: Lennon tends to adopt a 4-4-2 setup, but the suspicion is he may look to bolster his midfield options for Champions League matches, especially against top-quality opposition. That may see him using the 3-5-2 or 4-5-1 lineups he has tested in Scottish Premier League games over recent months.
Gary Hooper and summer signing Miku could form the basis of an attacking duo, with the former a viable option to lead the line alone as well.
The midfield will be crucial for Lennon, and he will look to captain and talisman Scott Brown to be both the heartbeat of the team and the destroyer attempting to ruffle the feathers of illustrious rivals. Powerhouse Kenyan Victor Wanyama is also vital in the Bhoys' engine room and, alongside Brown, he needs to do all he can to protect the Celtic defensive line, where fan favourite Charlie Mulgrew is a key man both offensively and defensively.
BIG HITTER: Gary Hooper
Lennon made an inspired signing when he snapped up this classy finisher from Scunthorpe United in July 2010, with his goal return in the two seasons since hugely impressive for a player who rose from the lower ranks of English football to the pinnacle of the Scottish game in double-quick time.
A scorer in the Champions League playoff tie against Helsingborg, his 29 goals last season were crucial in Celtic's title triumph and he has more than earned his right to mix it with the European elite this term. A clinical taker of chances when his confidence is flowing, this 24-year-old was heavily linked with a transfer to the English Premier League earlier this year, yet he insists he never wanted to leave Celtic.
CAPTAIN FANTASTIC: Scott Brown
Amid the influx of foreign players at Scotland's top clubs in recent years, there are a handful of traditional local products still thriving, and Brown is a shining example of an old-school midfielder who never shirks a challenge. After making his name with Hibernian, he moved to Celtic in 2007 and quickly confirmed his status as one of the finest ball-winning midfielders in Scotland while also retaining his ability to pick out a decisive pass.
Newcastle and Tottenham are among the Premier League clubs who have been linked with a move for his services in recent years, but he has stayed loyal to the Celtic cause and is rewarded with another crack at Champions League football.
NEW KID ON THE BLOCK: Miku
Nicolas Ladislao Fedor Flores, or Miku as he prefers to be called, is a name likely to be a name regularly inked onto the scoresheet during his season-long loan at Celtic from Spanish side Getafe.
A Venezuela international, his scoring return in La Liga suggests he should be more than potent enough to flourish in the modest Scottish Premier League, but Lennon has signed him primarily to add a touch of quality to his Champions League lineup.
"He is a powerful striker who we rate very highly," Lennon said. "It was a department we thought we were a little short and we believe we have signed a quality player in Miku."
SHOOTING STAR: Tony Watt
The teenage Scottish forward has made a big impression when handed first-team chances by Lennon, and he may be ready to cause some damage as an impact player coming off the bench in the Champions League.
His cameo display in the playoff victory against Helsingborg suggested the Scotland Under-21 starlet is getting a taste for high-profile European action, and he should gather more valuable experience in the Champions League group stages.
SECRET WEAPON: Emilio Izaguirre
This Honduran full back is a threat breaking forward, and his quality is confirmed by some of the clubs that have been linked with a move for him in recent years. Manchester United and Barcelona are said to be tracking his progress, and Celtic have done well to cling on to his speedy services.
Izaguirre spent a lengthy spell on the sidelines last season following a nasty ankle injury, but he is back and firing in time to take his place on the Champions League stage.
THE WEAK SPOT: As ever, making the transition from the increasingly weakened Scottish Premier League to Champions League football will be tough. Also, their record on their travels has been woeful in the group stages down the years, and that has to improve.
Striker Hooper is untested in this competition and, if he comes up short, there must be doubts over whether new boy Miku can score the goals Celtic require. Izaguirre may need to dampen his attacking verve to ensure the Celtic backline is secure, and there are also doubts about whether Lennon has what it takes to shine in this magical competition.
VERDICT: Third place in Group G is a decent target, but Celtic's away-day blues may mean they fall just short.