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.
Given that their 3-2 win in Moscow over a 10-man Spartak side was their first ever away win in 21 Champions League away trips it hardly augurs well for their visit to Lisbon and a Benfica team that still harbours hopes of qualifying themselves.
Celtic presently trail Barcelona by two points but hold a three point advantage over the Portuguese outfit while Spartak, who host the Spanish giants, are a further point adrift.
Lennon was relieved Celtic ended a run of three games without a win on Saturday when they beat Aberdeen 2-0 but said it had little relevance to the challenge facing them in the city where the Scottish side's predecessors became the first British club to lift the European Cup in 1967.
"This game will be our toughest in the group. We are going to come up against a very motivated team at home," Lennon said.
"They are very impressive at home and are going well domestically. They got a good result in their last game against Spartak and will be very motivated to beat us.
"We'll need to match their match their intensity of play. They'll come for us I'm sure in the first 15 or 20 minutes and we'll have to meet that head on.
Bayern can fancy their chances of taking something from the Valencia game as they have lost just once in their eight previous meetings with the Spanish side.
Valencia coach Mauricio Pellegrino, who will be relying on in-form striker Roberto Soldado to test the Bayern defence, summed up what the match meant to him.
"The match here against Bayern will be a final."