While it's far too early to write off Manchester City's Premier League title hopes, their Champions League dreams could be all but over for another season if they fail to beat CSKA Moscow on Wednesday night.
Failure to take maximum points would present Roma with the advantage in the race to second place in Group E, with Bayern Munich seemingly running away with top spot.
That makes Wednesday's clash one of the most important of Manuel Pellegrini's relatively short reign at City,meaning his team selection must be nothing short of perfect.
So far City have failed to get it right in Europe this season, taking just two points from a possible nine.
Defeat in Munich was harsh and Roma fought hard to claim a point at the Etihad, but the way in which Pellegrini's side let a two goal lead slip the last time these two met was simply unforgivable.
However, Sunday's derby win will breed confidence and a win against Russian opposition could be just the tonic for City.
Pellegrini will have to rely on the likes of Samir Nasri and Yaya Toure to provide the magic from midfield with the wizardry of David Silva absent due to a knee injury picked up by the Spaniard during the League Cup defeat to Newcastle.
Also watching on from the sidelines will be Aleksander Kolarov, who could be out for up to a month after suffering a calf injury during the warm up prior to the Manchester derby.
There is some good news on the injury front, with Frank Lampard back in contention following a thigh problem that has seen him sit out the last four matches. City only won once during Lampard's absence, and although the midfielder will not be ready to start, his return to the bench is a boost.
Goals win games
City have been vulnerable at the back this year, and Sunday's clean sheet was only their fourth in 15 games.
That's added pressure on the goalscoring shoulders of Sergio Aguero, and he'll need support against a CSKA side who are likely to sit back and attempt to soak up pressure.
Stevan Jovetic was given the nod against Manchester United, but Eden Dzeko will be desperate to return to the starting line up.
Neither have opened their account in Europe yet this season, but Pellegrini may opt for the clever moment and skill of Jovetic over Dzeko's power and hold-up play.
Midfield and defence
With City expected to dominate the game, defensive anchorman Fernando may be sacrificed for a more energetic and attack-minded midfielder such as James Milner or Fernandino.
Although Milner has spent the majority of his career out wide, he enjoys the responsiblity of a central role and has impressed when used in that position so far this season.
Out wide, you can expect Jesus Navas to be asked to cause problems with his pace, while Nasri will surely return to the starting XI after two substitute appearances.
At the back Gael Clichy will start at left back following a fine display against United and the absence of Kolarov while Martin Demichelis should retain his place after a solid performance on derby day.
Manchester City: Predicted Line-up
Hart; Zabaleta, Kompany, Demichelis, Clichy; Navas, Milner, Toure, Nasri; Jovetic, Aguero