Status: Premier League Champions, European Champions
Nickname: Red Devils
UEFA Ranking: 1st
THE RECORD: Manager Sir Alex Ferguson has long said United needed to add to their modest collection of two European Cups to confirm their status as a true football giant, so their dramatic triumph in Moscow last May was long overdue in his mind.
Now comes the challenge of defending their status as the finest side in Europe and this club will certainly not lack any desire in their pursuits.
COACH'S CORNER: Ferguson is a genuine living legend of the world game, with his 22-year stint as Manchester United manager yielding ten Premier League titles and domestic cups galore, yet it is his two Champions League titles that mean more to him than anything else.
The Scot's passion for success in this competition means he will be determined to have one final taste of European glory before his historic coaching career comes to an end and he is confident it can come this season. 'Manchester United should be in the latter stages of the Champions League every season and if you put yourself in position often enough, the chips should eventually fall your way,' he says. 'We had that against Chelsea in the Final last season and it could happen again this time.'
THE STAR TURN: Few would have put too much money on Cristiano Ronaldo appearing on the Manchester United section for this season's Champions League as Euro 2008 came to an end for Portugal, yet the world's most gifted footballer is still at Old Trafford and his return from injury cannot come soon enough.
He may have wanted to seal a move to Manchester United, but Old Trafford boss Ferguson refused to allow the jewel in his crown to leave and the Champions League holders will be a real threat again if he can recapture any of the form that saw him finish with an impressive 42 goals in all competitions last season.
THE NEW FACE: It took the best part of a year to broker the deal with Tottenham, but £30.75m took Dimitar Berbatov to Manchester United and the Bulgarian now has to light up the Champions League.
Even though he has appeared in the final of this competition as Bayer Leverkusen made their surprise run in 2002, he now gets his chance to prove he is a top level performer after being handed the No.9 shirt at Old Trafford. Oozing with skill and arrogance, Berbatov is a striker with the sort of unpredictable genius teams like United need and he should be a big hit playing alongside Wayne Rooney and Carlos Tevez.
THE WILD CARD: Tevez may not always steal the headlines for United, but the Argentine striker is the real unsung hero of this side. He simply doesn't understand the meaning of a lost cause, with his stamina and strength in a physical battle never ceasing to amaze.
Tevez's protracted transfer from West Ham in the summer of 2007 was shrouded in controversy due to the involvement of his controversial agent, but all the red tape was worth overcoming for United as this maker and taker of chances has been a big hit at United.
YOUNG GUN: Nani was hailed as the next Cristiano Ronaldo when United secured his services from Sporting Lisbon in the summer of 2007 and while he has yet to reach those lofty heights, this could be the season when he steps out of his compatriots considerable shadow.
Full of tricks on the wing, his close control and dribbling ability is still a little raw, so manager Ferguson will be hoping to shave off his rough edges over the course of this campaign.
WORD ON THE STREET: Wayne Rooney has not been at his best in a United shirt at the start of this season and some even suggested he was below par in their famous Premier League and Champions League double winning season last time around. Such criticism may be harsh, but the England striker will be desperate to answer those doubters this term.
There must also be some concern over the form and fitness of veteran United performers Gary Neville, Paul Scholes and Ryan Giggs. Can these 30-somethings sustain their efforts over the course of another long and arduous campaign?
VERDICT: Real contenders again, though much will depend on how Berbatov settles alongside Rooney, Ronaldo and Tevez. It is a mouth-watering prospect.
Status: Spanish league runners-up
Nickname: El Submarino Amarillo
UEFA Ranking: 11th
THE RECORD: A stunning second place in La Liga last season was a deserved reward for Villarreal as they capitalised on Barcelona's problems to snatch a lofty finish and guarantee entry into the Champions League group stages once again.
With their modest 25,000-capacity El Madrigal Stadium, the rise of this relative minnow has been a compelling story and now they have established themselves as one of the giants in Spanish football. Their most recent effort in the Champions League suggests they will be dangerous outsiders this season, as a run to the 2006 semi-finals so nearly ended with the ultimate glory only for a missed penalty against Arsenal to cost them dear.
COACH'S CORNER: Plucking coaches from South American football and expecting them to deliver on the European stage is not a familiar route to success, but Villarreal have hit the jackpot with Manuel Pellegrini.
A civil engineer who has succeeded in football, this former Universidad of Chile defender was capped by Chile at international level and enjoyed plenty of success in his coaching career with San Lorenzo and River Plate before arriving in La Liga and impressing all with his tactical acumen.
'We had some success last season, but I expect Villarreal to move on from here and feel confident that a return to the Champions League will help to raise our profile,' states Pellegrini. 'You cannot sit back and feel as if you have done well and always need to reach the next target.'
THE STAR TURN: Nihat Kahveci emerged from Euro 2008 with his reputation enhanced after he placed a crucial role in Turkey's stunning victory against the Czech Republic in the quarter-finals, but an injury sustained in the competition means Villarreal will be without their chief goal threat in the early stages of the Champions League.
Their hopes in the competition may depend on getting this energetic forward back to full fitness as quickly as possible. 'Finishing second in La Liga last season made us feels like winners and the fact that we are in the Champions League without a qualifier is an amazing reward,' says Nihat.
THE NEW FACE: Villarreal's rise as a European force was confirmed when they managed to lure Barcelona's Brazilian star Edmilson to the club this summer and his arrival will give them the experience and class they will need in the Champions League.
A title winner with Lyon and Barcelona, he brings huge helpings of experience to the party and he is also a seasoned international who has seen everything in the game. 'We have signed a champion,' was the praise from Villarreal coach Manuel Pellegrini.
THE WILD CARD: The veteran Robert Pires is a classy performer when fit and at his peak, but the former Arsenal man was not able to show his best form during his first season in Spain as he damaged knee ligaments before the season kicked off.
A respected figure in the game, this French international proved his worth last season as he helped the club to their lofty finish in La Liga and even though he will celebrate his 35th birthday during the group stages of the Champions League, he is still a major creative threat down the flank.
YOUNG GUN: Jozy Altidore was always destined for Europe after making a big impression with the New York Red Bulls and after rumours of a move to the English Premier League, the American teenager finally signed for Villarreal in June. In doing so, he became the most expensive export from the MLS with an $8m price tag.
Rumour has it that Villarreal have considered sending this gifted star out on loan to gain experience of the European game this season, though he is expected to stay put for now.
WORD ON THE STREET: Is the only way down for Villarreal? Their stunning second place finish in La Liga last season will surely be tough to build on if Barcelona are revived as many expect them to be under new coach Pep Guardiola. A dip in form at home could affect their Champions League form.
You need to have real belief to succeed in the Champions League and while Manuel Pellegrini is a top coach, you still get a feeling that some Villarreal followers are pinching themselves as they struggle comprehend the success their club is enjoying.
VERDICT: A place in the quarter-finals is the best they can hope for.
Status: Scottish champions
Nickname: The Bhoys
UEFA Ranking: 22nd
THE RECORD: The 1967 European champions have proved they can be a match for anyone on their Parkhead pitch, yet their record on the road is as woeful as the most hopeless of amateurs playing park football on a Sunday.
The passionate and intimidating atmosphere the Celtic fans generate in Glasgow has seen them record victories over the likes of AC Milan and Manchester United in recent editions of the Champions League and the Bhoys will be a real threat if they can find a way of adding points away from Scotland.
COACH'S CORNER: Gordon Strachan was tipped by many to leave Celtic after he led the club to an unlikely third successive Scottish Premier League title last season, yet the fiery Scot remains in position and he will be hoping to build on a fine record of successive appearances in the last 16 of the Champions League.
'A European night at Parkhead is something very special and while we might not be as technically gifted, we can match anyone on our own pitch,' says the former Manchester United midfielder. 'However, we need to find a method of performing better away from home as our record on the road just isn't good enough. Tactically and technically we can improve.'
THE STAR TURN: Artur Boruc was a star for Celtic throughout their Champions League run last season and the Polish stopper is still a key man in Strachan's squad despite talk of a summer move to one of the top clubs in Italy's Serie A or Premier League giants Arsenal.
He can be an inspired shot-stopper and as it is difficult to keep top quality performers in the less than competitive Scottish league, Celtic have done well to hang on to Boruc. 'I'm happy at Celtic and while anyone would be flattered to be linked with clubs like Juventus and Arsenal, I'm happy to stay,' he confirms.
THE NEW FACE: Georgios Samaras struggled to make his mark during a less than successful stint in the English Premier League with Manchester City, but the Greek hit-man rediscovered his scoring touch during a loan stint at Celtic last season and made the move permanent during the summer.
'I do not see moving to Scotland as a step down because Celtic have a good record in Europe over the last few years,' says Samaras. 'You have to have dreams and then miracles can happen, so we have to look at getting beyond the last 16 of the Champions League this season.'
THE WILD CARD: Japanese star Shunsuke Nakamura was the inspiration behind Celtic's win against Manchester United in the 2006/07 Champions League group stages and his prowess from set-pieces will be vital for Gordon Strachan, if he can keep Nakamura fully fit in the months ahead.
One of the biggest success stories of Japanese football, Nakamura made his name with Reggina in Italy before sealing a switch to Scotland and he has become a firm favourite of the Parkhead faithful.
YOUNG GUN: While Aiden McGeady may only be 22, his experience is that of a seasoned professional and the Irish winger needs to confirm his class in the Champions League this season.
Flashes of inspiration at Parkhead against some of Europe's best suggest McGeady is capable of firing on the biggest stage in club football, yet his consistency has not always been there when Celtic are on the back foot in away matches. His skills and pace on the break should be a threat as Strachan's side tries to soak up the pressure.
WORD ON THE STREET: Celtic use defensive tactics away from home and even though the negative tactics have come close to snatching a couple of draws against top sides, their lack of creative intent means they will continue to rely on home form to give them any chance of qualifying.
A heavy reliance on Jan Vennegoor of Hesselink and Nakamura is all the more obvious when one or both are on the sidelines and Strachan will need his star names to finally stand up in their three group away games. 'It has become a mental thing for Celtic at this stage as they just don't believe they can get anything in away games,' confirms former Celtic striker John Hartson.
VERDICT: Their home has been amazing in the last few years, yet many of their wins have come with a touch of fortune attached. It's hard to see them getting through the group phase this time.
Status: Danish champions
UEFA Ranking: 30th
THE RECORD: Their last appearance in this competition was way back in the 1995/96 season. They were initially beaten in the qualifiers by Dynamo Kiev, only to be reprieved after the latter became involved in a bribery scandal.
Back then, they beat Panathinaikos of Greece and drew with FC Porto, but still finished bottom of their pool and will be hoping for better this time around.
COACH'S CORNER: A boss with extensive experience in England with Middlesbrough, Millwall, Bolton, Arsenal, Norwich and Wigan, Bruce Rioch took over at Aalborg this summer following the departure of title-winning coach Erik Hamren for Rosenborg in Norway. Rioch is no stranger to the Danish game; from 2005 to 2007 he was on the bridge at Odense, notably steering them to third place in the Superliga in his first season in charge.
In a playing career which took him to Luton, Aston Villa, Derby and Everton, Rioch was a dynamic midfielder with a blistering left-foot shot. Although born in England, he qualified to play for Scotland through his father's birthplace and he captained the 'Tartan Army' at the 1978 World Cup finals in Argentina.
'We must face two of the biggest clubs in the world in Manchester United and Celtic, plus a very capable Villarreal,' says Rioch. 'It's a learning curve for us and a great opportunity for us to show what we are made of.'
THE STAR TURN: Jeppe Curth was the top scorer in the Danish League last season with 17 goals. Opportunistic, powerful in the air and bristling with determination, he needs to be watched very carefully indeed. Once an attacking midfielder, he has represented his country at all levels from Under 16 to Under 21.
He came up through the youth ranks of top Dutch side Feyenoord and despite being voted Denmark's Talent of the Year in 2002, he found it difficult to convince his club coaches that he was worthy of a first team berth and after an injury-hit year on loan to Rotterdam's third side Excelsior, he moved back to his homeland to play for Aalborg.
THE NEW FACE: Danish international right-back Kasper Bogelund took the decision to return to the mother country this summer after a decade in Holland and Germany with PSV Eindhoven and Borussia Monchengladbach. He only played in a handful of games as Gladbach won promotion to the Bundesliga last season and was glad to move on a free transfer.
Twice a Dutch League winner with PSV (2003, 2005), he earned 15 senior caps for Denmark, appearing at both the 2002 World Cup and Euro 2004. Goals are not a speciality, but he did score the German Goal of the Season in 2005, an incredible long-range effort against Schalke.
THE WILD CARD: A little firecracker of a right-sided midfielder or forward, Caca is the younger brother of the Brazilian left-back Dede, who has starred at Borussia Dortmund for several years. After starting out in Brazil with Sao Paulo and Atletico Mineiro, Caca was recommended to Bundesliga side MSV Duisburg by his sibling in 2003, yet the move did not work out and he retraced his steps, pulling on the shirt of Mineiro again, as well as Clube de Regatas.
A second stab at European football with Aalborg, whom he joined in 2006, has gone much better. He was a member of the Brazilian Under-17 side which claimed the world title in 1999. One of his team mates was a certain Inter Milan striker named Adriano.
YOUNG GUN: Thomas Enevoldsen is a high-energy, tactically-aware midfielder who has been a mainstay of various Young Denmark elevens. The son of former Aalborg star Peter Eneveldsen, he is under contract until 2010 but that has not prevented him being linked with a transfer to England, with West Ham apparently interested.
His moment in the European sun came last year in a UEFA Cup tie away to Tottenham Hotspur at White Hart Lane, cutting in from the left to unleash a 25-yard screamer past Paul Robinson.
WORD ON THE STREET: An undoubted positive is Moroccan keeper Karim Zaza, who is as fine a shot-stopper as there is in Scandinavia. With him as their last line of defence, Aalborg form a compact, cohesive unit and have the competitive edge which Rioch exhibited as a player. Thomas Augustinussen is both a good organiser and solid ball-winner in front of the back-four.
Curth aside, there simply is not enough firepower in the side to trouble the European big boys. They are lacking creativity and too often they simply launch a high approximate ball into the box.
VERDICT: The Jutland team look odds on to come dead last in a group in which Manchester United, Celtic and Villarreal will hold sway.