Despite woeful form in the league, Manchester United have done well in the Champions League this season, having finished top of their qualifying group with four wins out of six.
Olympiakos finished second in their group behind PSG after qualifying ahead of Benfica on goal difference. Three wins out of six is a good return and they were desperately unlucky not to get a point in Paris, with Edison Cavani scoring an injury time equaliser.
Tuesday night's game will be United's fifth game against the Greek champions, but what happened in the previous meetings?
The first time Manchester United played against Olympiakos there was an attendance over 73,000 in Athens.
United's starting line-up consisted of Fabien Barthez, Gary Neville, Ronny Johnsen, Laurent Blanc, Denis Irwin, David Beckham, Paul Scholes, Juan Sebastian Veron, Roy Keane, Ryan Giggs and Ruud van Nistelrooy.
Four days earlier, Beckham scored that goal for England against Greece to book their place in the 2002 World Cup final. He must have really had it in for the Greeks that season, with him putting United 1-0 up with over an hour played, after an inviting cross from Giggs.
With Sir Alex Ferguson keen to ensure United left with a victory, he replaced Veron with Andy Cole, who scored less than two minutes after coming on, playing a nice one-two with Giggs.
United struggled to get off the mark in the game at Old Trafford but appeared to be given a great opportunity to break the deadlock when they won a penalty with over an hour played. Van Nistelrooy saw his penalty saved though.
It was Solskjaer who put United 1-0 up but they had to wait until there were just ten minutes remaining. Van Nistelrooy made amends for his penalty miss by creating the goal.
Two minutes remaining, Giggs made it 2-0 thanks to a beautiful ball forward from Veron.
After managing to keep United out all game, the Greeks collapsed and allowed van Nistelrooy to make it 3-0 in injury time.
United went through to the next round after finishing second in the group on goal difference. Olympiakos finished bottom of the group, having won just one game from six.
United were drawn in the same Champions League group as Olympiakos in consecutive years and their first game this season came at Old Trafford.
Barthez, Neville, Mikael Silvestre, Veron, Rio Ferdinand, Blanc, Beckham, Nicky Butt, Scholes, Giggs and
Solskjaer made up the starting line-up.
With less than 20 minutes played, Giggs put United in front after getting on the end of a cross in from Scholes. Five minutes later, Veron doubled United's lead, after racing behind the Greek defence and chipping the goalkeeper.
The last meeting between the two clubs was the most competitive to date, with United having to work very hard for their three points.
It started off with it looking as though it would be business as usual for United, as they went 2-0 up with an hour played. Blanc got onto the end of a corner from Giggs, before Veron struck from distance.
United went on to concede two goals in four minutes and with just five minutes left to play they were still drawing.
Then, the ball fell to Scholes on the edge of the box and the goalkeeper could only get a hand to it, but not enough to keep the shot out.
United topped the group with five wins out of six, whilst Olympiakos finished bottom of the group.