Champion’s league games are big at the best of times but tonight are bigger than most for Manchester United who may have to win this competition if they are to play in next season.
If they are to win they’ll have to do it without Nani, Evans and Jones who are missing out , Juan Mata is cup tied.
Olymiakos are 20 points clear at the top of their league and are unbeaten domestically although United have won all four of the clubs' past encounters, which came in the 2001/02 and 2002/03 first group stages.
Ryan Giggs has featured every time, scoring three goals.
Newstalk's European football correspondent Graham Hunter spoke to Oisin Langan about tonight's tie.