While plenty of eyes will be fixed upon the marquee CL fixtures this week -- Juventus' trip to Real Madrid and Arsenal versus Borussia Dortmund, to name just two -- there is intrigue to be found all over the fixture list.
Can Kaka recover in time?
Once again, two of the biggest teams in Champions League history come face-to-face when Barcelona visit AC Milan Tuesday, but there could be a different -- and familiar -- face in the Italian lineup from last year.
Last season, Barcelona overturned a 2-0 first-leg deficit to win 4-0 at the Camp Nou on their way to the semifinals to prove that they could turn around a losing position, and they have had the best of previous meetings between the sides, as Milan's win had been their first over the Catalan team since October 2004.
One of the stars in midfield for AC that day was a young Kaka, who had only recently joined the club from Sao Paulo. He would go on to become one of their greatest-ever players and now looks like he could be given a chance to impress again if he can prove his fitness ahead of the tie.
The Brazilian is a long way from the player who picked up the Ballon d’Or in 2007 but, after a spell with Real Madrid, he will be well-placed to find a spot in midfield when Barca come calling. The only issue is his fitness after succumbing to a thigh injury shortly after rejoining the club on transfer deadline day.
"I don't know if Kaka will be able to play from the beginning in the match against Barcelona," Milan coach Massimiliano Allegri said. "He made a good performance [against Udinese on Saturday]. Kaka is an extraordinary player. He has to fully recover since he had to stop for 40 days due to a muscle injury. He only played 20 minutes in a midweek match."
One the injury front, the San Siro side are clearly struggling. The absence of Mario Balotelli already makes it a tough task for them -- the striker won and scored a penalty in the fourth minute of second-half injury time against Ajax to ensure Milan remained second in Group H on four points -- and there are also others to consider. Goalkeeper Christian Abbiati, defenders Daniele Bonera and Mattia De Sciglio, and forwards Stephan El Shaarawy and Giampaolo Pazzini are all in the treatment room, making it a lengthy list for the Italians to overcome.
If he can recover in time, Kaka could find himself well suited to the role of "White Knight". Milan will certainly need one if they are to slay the Catalan dragon.
-- Jon Molyneux-Carter
Coping without Kompany
Their 3-1 win over West Ham at the weekend wasn't exactly the hardest test of their defensive nous, but Manchester City are another team who are struggling with injury concerns. City's main issue is at centre-back, with manager Manuel Pellegrini left with only two senior specialists available in that position: Matija Nastasic and Joleon Lescott.
As proved at Upton Park, midfielder Javi Garcia is an option, but it's not one that City want to be relying on for long and seems an odd situation to find themselves in given the spending power at their disposal.
Pellegrini clearly doesn't view Micah Richards as a centre-back -- which has been as confusing to the England youngster as many others -- but there is perhaps a feeling that solidity at the back is only important if the goals up front dry up.
With no sign of that happening any time soon given how impressive Sergio Aguero has looked in recent weeks, City can take on Wednesday's trip to CSKA Moscow knowing that their attack can help to bail them out, but complacency is a dangerous thing at this level.
Back in August, there was no sign City would take this game lightly, as director of football Txiki Begiristain told Sky Sports News: "We have to be respectful of all the clubs. They are champions of the Russian league and have good players but we have a lot of confidence."
And if they need further motivation, then all they need to do is take a look at their woeful away record in Europe over the past two seasons: just one win and five defeats in six games.
While there is some free-flowing football in the final third, last month's battering by Bayern has City's defence rocking in Europe, so this game takes on even more importance. Without Kompany steadying the helm, they have not looked solid and will be under pressure to tighten up in Russia if they don't want to hand CSKA the advantage at this early stage.
-- Jon Molyneux-Carter
Schalke, take a bow
When initially drawn, Group E looked generous for Chelsea: a pair of prickly yet flawed opponents in Basel and Schalke plus the relatively flair-less Steaua Bucharest.
Yet the first two matchdays riled things up -- namely, the Blues' home defeat to Basel -- to the point that this is no longer a cakewalk. The Romanian side excepted, escaping this group never looked so uncertain.
To wit, Schalke -- Chelsea's opponents on Tuesday in Germany. To date, Schalke's season has been one of Everests and ocean floors: nine goals conceded in their first three Bundesliga games was followed by an eye-opening 2-0 win versus Leverkusen. Then a big win versus Steaua on CL Matchday 1 preceded a harrowing 4-0 defeat to Bayern. One step forwards, two back.
This past weekend saw much of that same disorientation from the Royal Blues, forced as they were to scramble for an entertaining 3-2 comeback win at lowly Eintracht Braunschweig thanks to Roman Neustadter's 90th-minute winner.
The Schalke stats are grim, with 19 goals conceded in nine league games -- the fifth-leakiest defence in the German top flight. The injury situation makes it seem even worse: a season-ending cruciate ligament tear for holding midfielder Marco Hoeger and fresh knee surgery for Klaas-Jan Huntelaar.
That said, this is Group E, the group of chaos. There is quality and good luck in the Germans' ranks. Jermaine Jones, Kevin-Prince Boateng and Timo Hildebrand are all fit again and more than capable of thwarting Jose Mourinho's men.
There is the constant danger of Julian Draxler, a perennial transfer target for various Premier League clubs. Jefferson Farfan offers tireless industry on the flank, whether servicing Huntelaar -- prior to his injury -- or the emerging threat of Adam Szalai.
If nothing else, Schalke are entertaining to watch whether scoring four or conceding four. Expect more of the same at Veltins-Arena on Tuesday.
-- James Tyler