Juventus v Real Madrid (Tuesday) - Sky Sports 4 (19:30), Sky Sports 4 HD (19:30)
Things have got rather sticky for Juventus. After sauntering along facilmente strada for the best part of two years in Serie A without any real threat to their Scudetto title challenge, Juve now sit behind both Napoli and Roma.
In the Champions League, the short-term future looks bleaker still. After draws against FC Copenhagen and Galatasaray and defeat to Real Madrid in the Bernabeu, the Old Lady now rather need to beat Carlo Ancelotti's side at home. Even a draw would likely lead to a four-point gap to Galatasaray above them, meaning that a win would be required in the Ataturk Stadium. It doesn't look good.
Thankfully, Real aren't on particularly handy Champions League form. Just 12 goals in three games (and three wins) this season. And, mercifully, Ronaldo doesn't seem to fancy it either. Just seven goals in those three matches, and 19 since the beginning of last season. Good luck.
Olympiakos v Benfica (Tuesday) - Sky Sports 4 - Red Button (19:45)
This is not just a match of two teams level in second and third, sat behind a mesmerising Paris St Germain and in front of an out-of-their-depth Anderlecht. This is not just a match that will surely decide which club will make it beyond the group stage and which will become fourth of fifth favourites for the Europa League. Oh no, this is a chance for Greek redemption.
One understands the urgency from UEFA to complete the match, but it ended in complete farce, and Olympiakos should consider themselves incredibly unfortunate not to finish as victors and thus take control of the group. At 1-0 up, amidst a storm of frankly biblical proportions, David Fuster rolled the ball into an empty net, only to see it stop in a puddle before reaching the line. Oscar Cardozo then rescued a last minute point for Benfica. And so, in Athens, one suspects that Michel's side will be ready for revenge in their bid to reach the knockout stages for just the third time since 1999.
Both sides can certainly rely on imperious league form. Benfica have lost two in 43 in Portugal, whilst Olympiakos go better, losing one in 42. Three defeats in 85 games - such figures are just silly. One thing is for certain, the victor on Tuesday will have one foot in the knockout stage.
Manchester City v CSKA Moscow (Tuesday) - Sky Sports 2 HD (19:00)
For both pleasant and not so pleasant reasons, it will be well worth tuning in to this one. At the most basic level, if City win, as they should do, they will be all-but qualified for the knockout rounds of the Champions League for the first time. That still seems a little odd, given their confirmed status as an established power in English football, but then again they did have Roberto Mancini in charge for their previous two campaigns.
One also presumes the telly chaps will put an additional couple of effects microphones near the CSKA fans, if only to ensure that, if any fresh racisms do occur, they will be able to play it back to their clearly hard-of-hearing staff. "We did not hear any racial slurs, so it is difficult to comment," said CSKA boss Leonid Slutsky before this game.
Finally, Manuel Pellegrini will, for reasons beyond the obvious, be hoping that Costel Pantimilon doesn't drop a clanger or two, because that would leave him with quite the quandary for City's Premier League game with Sunderland at the weekend.
Dortmund v Arsenal (Wednesday) - Sky Sports 1 HD (18:00)
24 hours before Arsenal were busy overrunning Liverpool's midfield, Dortmund were shellacking Stuttgart 6-1, with that man Robert Lewandowski bagging a juicy hat trick - this is a side that very much mean business.
After the late defeat at the Emirates a fortnight ago, Arsene Wenger is left with an interesting dichotomy. Does he approach the game with the mind-set of playing for a point given Dortmund's strength, or put trust in his side's ability to attack with as much fluidity as they have done for large periods of 2013?
The answer probably lies somewhere in between, but let us just say that if Arsenal are drawing 1-1 with ten minutes to go, we can't see Monsieur Wenger imploring his side to stream forward with such vigour as two weeks ago. They're good on the counter, these Klopp boys.
Ajax v Celtic (Wednesday) - Sky Sports 4 (19:30), Sky Sports 4 HD (19:30)
When the draw was made for the Champions League group stage, Celtic fans would surely have taken Europa League involvement beyond Christmas as a success story, such was the size of the club's task. However, the regression in Milan under Massimo Allegri means that Neil Lennon's still have a squeak at qualifying for the knockout stage. Nevertheless, if we are to assume that a trip to the Nou Camp will end in defeat, Celtic must surely win their next two games, starting in Amsterdam on Wednesday.
You probably know the drill by now. Celtic have won one away Champions League proper match in twelve years, so often the undermining of potential European progress. In that time they have beaten Barcelona, Milan, Manchester United and Juventus at Celtic Park, but just Spartak Moscow on the road.
Something has to give, and Ajax are there for the taking. Already effectively eliminated after defeat in Glasgow a fortnight ago, Frank De Boer's side are without a win in three league games and lost at home to Vitesse on Saturday, now sitting sixth in the Eredivisie. Can Celtic end their away day European hoodoo?