Liverpool boss Brendan Rodgers faces perhaps the biggest match of his time in charge at Anfield this evening as his side go up against the mighty Real Madrid at the Bernabeu - and it looks as though he may be about to make the biggest decision of his career.
Reports leading up to the game suggest that that Liverpool boss will drop his captain Steven Gerrard for the Group B showdown, days after the 34-year-old suggested in an interview that he may be on his way out of Anfield at the end of the season.
If that does prove to be the case then Liverpool will go up against the most in-form team in Europe without their most experienced performer - although Rodgers says the decision could be made with their Premier League clash against Chelsea on Saturday in mind.
There could be some logic to the decision too; Gerrard isn't the most mobile anymore and has been operating at the base of midfield this season, with Gareth Bale and Cristiano Ronaldo - who could become the Champions League's all-time top scorer - on the charge and with James Rodriguez pulling the strings, the Reds may opt for a more energetic option to act as a shield like Jordan Henderson, with perhaps Emre Can coming in as an attacking alternative.
The fact that Bale is back from injury will further add to Rodgers' problems. He hasn't played since early October, but is now fit and raring to go. "He's ready to play. I don't know if he will play from the off or on the bench," said boss Carlo Ancelotti.
Liverpool's own talisman, Daniel Sturridge, has travelled to Madrid for the game but won't take part as he continues his recovery from injury in time to take part.
Arsenal meanwhile narrowly avoided a major upset in their last game against Anderlecht and will hope for a much more straight-forward win this time round. Late strikes from Lukas Podolski and Kieran Gibbs saved Arsene Wenger's blushes in Belgium and a win at the Emirates Stadium this time round will help the Gunners move one step closer to qualification for the knockout stages once more.
They will be without Jack Wilshere for the game, but Theo Walcott made his comeback against Burnely at the weekend and could feature, while Mathieu Debuchy and Olivier Giroud are close to making their comebacks.
Elsewhere in Europe, Borussia Dortmund will look to put their domestic woes behind them when they take on Galatasaray in a bid to take control of their group. Finally, Juventus go up against Olympiakos, Malmo face Atletico Madrid, and Basel go head to head with Ludogorets. The final two fixtures see Zenit St. Petersburg and Benfica take on Bayer Leverkusen and Monaco respectively.