Holders Chelsea and Scottish champions Celtic can seal their places in the last 16 of the Champions League on Tuesday but they will have to do it the hard way by winning away from home.
Chelsea's task looks harder as they travel to Serie A leaders Juventus but Celtic's away form in the Champions League is woeful so they will have to repeat their outstanding performance in the home win over Barcelona against a talented Benfica side.
Bayern Munich, the side that Chelsea beat on penalties in last season's final, also have a tricky trip to Spanish side Valencia, in a rematch of the 2001 final which the Germans won in a penalty shootout.
Bayern and Valencia are locked on nine points apiece, but with Belarus side BATE Borisov breathing down their necks on six points and all but guaranteed three points when they host pointless and hapless French side Lille neither can afford a slip-up.
A win for either Valencia or Bayern would see the victor join the one side playing on Tuesday already assured of a place in the last 16, Manchester United, who are also certain to top their group.
Chelsea have made hard work of their group, with a fortunate last minute win over the highly-talented Shakhtar Donetsk last time out setting them up nicely for the trip to Turin.
However, they come into it in the worst possible fashion having been beaten by West Brom, managed by former Chelsea coach Steve Clarke, on Saturday and having taken just two points from their last 12 in the Premier League.
Chelsea boss Roberto di Matteo admitted he would have to rein in his more expansive tactics he has used this season as his defence was becoming an increasing worry.
"We have played differently this season, but we might have to go a little bit tighter to win games and make sure we don't concede," he said.
"Maybe it is time to look at it, change it, and get a win. We have massive games coming up, but we have players with a lot of experience in these situations.
"We will look at the set-up of the team and maybe sacrifice a little of the attacking options."
With Shakhtar - who trail Juventus and Chelsea by a point - likely to come away with three points when they play minnows Nordsjaelland in Copenhagen, it is vital for the holders to take if not the win then at least a point from the Italian champions.
Celtic's victory over Barcelona restored the 'thunder' to Parkhead according to manager Neil Lennon, but that will be quickly forgotten should they fail to progress to the knockout stages.
Tuesday (kick-offs 1945GMT unless stated):
Nordsjaelland (DEN) v Shakhtar Donetsk (UKR), Juventus (ITA) v Chelsea (ENG), BATE Borisov (BLR) v Lille (FRA) (1700), Valencia (ESP) v Bayern Munich (GER), Spartak Moscow (RUS) v Barcelona (ESP) (1700), Benfica (POR) v Celtic (SCO), Galatasaray (TUR) v Manchester United (ENG),
Cluj (ROM) v Braga (POR)