Reigning European champions Manchester United can join Barcelona and Sporting Lisbon in the knockout stages of the Champions League with victory at Celtic, while Bayern Munich and Arsenal also have a chance to qualify for the last 16.
A win for Sir Alex Ferguson's team in his home city of Glasgow would send United through with two games to spare if Group E rivals AaB Alborg fail to beat Villarreal in Denmark and a draw would be enough if the Spaniards win.
Celtic have been playing down their chances in Wednesday night's match at Parkhead but Scotland captain Darren Fletcher has warned his United team-mates not to believe the defeatist talk emanating from the Scottish club's camp.
"You have to take everything they say with a pinch of salt," Fletcher said. "I know some of the Scottish players in the Celtic team. Although they respect the opposition, on their day they feel as though they can beat anyone."
"They are building us up now but when the match starts, all reputations will be put to one side because they want our scalp."
United defenders Gary Neville and Wes Brown are both on the injured list so teenage Brazilian Rafael is likely to start at right-back. Ferguson must also choose whether to play Tomasz Kuszczak or Ben Foster in goal after deciding to rest 'keeper Edwin van der Sar.
In Group G, injury-plagued leaders Arsenal will go through if they beat last-placed Fenerbahce at the Emirates but will miss strikers Emmanuel Adebayor and Theo Walcott plus defenders Emmanuel Eboue and William Gallas, who are all out with injury.
Walcott and Adebayor were both injured in a physical Premier League defeat with Stoke City at the weekend and manager Arsene Wenger is eager to get back to winning ways and qualify for the last 16 of the Champions League so he can rest some players.
Wenger said: "We have not been efficient recently with our results in the last two games and that is why it is important to come back and win. I believe that once you qualify in the Champions League you can be completely focused and, if needed, rest some players in the Champions League."
Nicklas Bendtner and Robin van Persie are expected to start up front for the Gunners.
Meanwhile, nine-times European champions Real Madrid welcome back striker Ruud van Nistelrooy and defender Pepe from injury to help avenge their 2-1 defeat at Group H rivals Juventus two weeks ago when they play the Italians at the Bernabeu.
Bayern, who head Group F on seven points ahead of Lyon on five, travel to third-placed Fiorentina, who have two points.