After a couple weeks away following the international break, the Champions League is back, and there are some potentially enthralling matches to look out for. Here are some of the major talking points in the build-up to the key games on Tuesday night.
Schalke vs. Chelsea: Mourinho's Selection Headache
It is not exactly a secret that Jose Mourinho doesn't know what his best team is. I mean, he even said so himself.
Having started Chelsea's last five games, it seemed as though David Luiz had established himself as John Terry's regular defensive partner. Following his quite comical error against Cardiff on Saturday afternoon, however, this may no longer be the case.
In an attacking midfield sense, it seems like it is now just Eden Hazard then two others picked randomly out of a hat. Juan Mata seemed to be working his way back into the Special One's favour before being unceremoniously hooked off after 59 minutes against Cardiff, with the game still at 1-1.
The thought of the diminutive Spaniard being taken off at such a key stage in a game in the last two years would have been unthinkable. That is no longer the case.
Hazard, Oscar and Andre Schurrle are the trio I'd predict as Mourinho's selections against Schalke. But then you're still leaving out Mata, Kevin de Bruyne and Willian. He could also just as easily play Ramires further forward.
I did say it was a headache.
Arsenal vs. Borussia Dortmund: Mesut Ozil and Santi Cazorla
In what is probably the most enticing game of the evening, there are many intriguing points to discuss. But the continued development of potentially the most exciting creative partnership in Europe is top of the agenda.
When Arsenal signed Mesut Ozil, the only (very, very slight) criticism you heard from anywhere was that the Gunners were already overloaded with attacking midfield options and should have been strengthening elsewhere.
The finest of all these options was the wonderful Santi Cazorla, undoubtedly Arsenal's standout player of last season. Criticism of Arsene Wenger now seems like a distant memory.
The partnership began in earnest on Saturday afternoon against Norwich when Cazorla was fit to start alongside Ozil for the first time. Whilst both were capable of playing in multiple attacking roles, Wenger chose to start Cazorla from the right and Ozil through the middle.
Interestingly enough, Ozil actually spent far more time drifting right and combining with Jack Wilshere than left to combine with Cazorla. I'd imagine these were instructions from Wenger so that they didn't get in each other's way.
Borussia Dortmund on Tuesday night will obviously provide a far sterner test than Norwich did, and it will be interesting to see if Wenger can utilize the two players effectively without compromising Arsenal defensively.
If he can get the very best out of both of them, it could be a rather frightening proposition.
Austria Vienna vs. Atletico Madrid: Can Atletico Bounce Back?
Atletico Madrid had been riding on the crest of a wave for the most of the season.
Having coped easily with the loss of Radamel Falcao, they had a 100 per cent record in every competition, were sitting joint top of La Liga and were fresh from beating Real Madrid at the Bernebau for the second time in as many games.
Then, late on Saturday night, it all went a bit wobbly. Barcelona surprisingly dropped points for the first time away at struggling Osasuna, leaving the way clear for Atletico to go top with a win away at Espanyol. They choked, losing 1-0.
Now, they have an eminently winnable game away at Austria Vienna, which would take them onto nine points and to within touching distance of their first appearance in the knockout stages since 2009.
Let's hope they can regather themselves and keep going, as it would be great to see another Spanish team challenging other than either of the El Clasico pair.
AC Milan vs. Barcelona. Yes, it's these two again.
The game on Tuesday night between these two powerhouses of European football will be the seventh time these two have met in the Champions League since the start of the 2011 season.
Last season's encounter certainly provided some fireworks—goals from Kevin-Prince Boateng and Sulley Muntari put Barcelona to the sword with a 2-0 win at the San Siro before Barcelona bounced back with a masterful 4-0 victory in the second leg to put them through.
The Catalan giants became the first club to recover from a 2-0 first leg deficit in Champions League history in the process. Not bad.
There have been 19 goals in the last six meetings between these two sides, so hopefully there will be more of the same tonight.
It will also be interesting to see how Barcelona cope should Lionel Messi still not be fit to play. Barcelona are far from being a one-mean team, but they do struggle obviously without him. As any team deprived of such a great player obviously would.