Winning the Champions League has never been more important for Manchester United. Just to get a chance to rejoin Europe's elite again.
With United in an unusually lowly Premier League position, 11 points from the fourth Champions League place, qualifying for next season's Champions League through the usual domestic route seems unlikely.
So David Moyes' side wants to build a strong first-leg lead at Olympiakos on Tuesday to smooth the passage to the quarterfinals. And beyond, given how essential winning the May final is to the club's pride and global standings.
Here are five things to know about Tuesday's round of 16 game in Greece:
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RESPITE IN EUROPE
If only United's European form had been replicated domestically, it wouldn't be so bleak for Moyes during his first season in charge.
In the Premier League, United is meekly surrendering the trophy, sitting in sixth place, only ahead of Everton on goal difference and having played an extra game.
But United eased through the Champions League group stage with four wins, including an eye-catching 5-0 rout at Bayer Leverkusen, and two draws. Going through as group winner ensured the three-time European champion avoided potentially trickier teams at the start of the knockout phase.
"Teams don't want to play Manchester United," Moyes said. "They know what it stands for as they have been successful. I hope we can play well enough to get through this round and see what happens next."
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CONSTRASTING FORM
While it's miserable for United domestically, Olympiakos is unstoppable, sitting 23 points clear at the top of the Greek Super League. Just nine goals have been conceded in 26 games.
"They are undoubtedly the best team in Greece, no question about it," Moyes said. "They also have a lot of Greek internationals who will go to the World Cup and it will be a really tough game."
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STOP ROONEY
Olympiakos has lost all four previous encounters with United, and knows any chance of a reversal in fortunes hinges on stopping strikers Robin van Persie and Wayne Rooney. Both scored on Saturday as United ended a three-match winless run in the league by beating Crystal Palace 2-0. And Rooney travels to Greece with his future settled, having signed a lucrative new United deal through 2019 on Friday.
"The team will be very proud if they can stop Rooney and Van Persie scoring, Olympiakos director Pierre Issa said. "It's a challenge to stop them. We will have to work hard."
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STRIKER SHORTAGE
Where will Olympiakos' goals come from? There are just two fit strikers: Michael Olaitan and Nelson Valdez.
Top scorer Javier Saviola is out of Tusday's game with a thigh injury he sustained in the 4-0 win at OFI Crete on Saturday, and Konstantinos Mitroglou joined Fulham last month,
"Mitroglou was a really good goalscorer for them and a main player," Moyes said. "Does it weaken them? I think they'd rather have him than not but probably felt the offer was so good they had to take it. Since then, they've brought in two or three other players as well and I couldn't be sure who will and won't play."
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RACISM IN THE STANDS
UEFA will be keeping a close eye on the Olympiakos supporters on Tuesday after racist behavior by some during the final group stage match against Anderlecht led to UEFA sanctions.
The lower tier of the north stand at Karaiskakis Stadium will be closed as punishment, and further racism could lead to the entire stadium being closed to fans for the next UEFA fixture.