David Moyes will be happy with few of his players after their defeat in Athens. Here's how they fared:
DAVID DE GEA: Wrong-footed for first goal. Could do little about the second. 5/10.
CHRIS SMALLING: Slipped on a number of occasions. Was supposed to offer more security than Rafael but he was casual on the ball and lost the ability to tackle. 4.
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RIO FERDINAND: Lack of pace uncovered again. 5.
NEMANJA VIDIC: The only United defender to stand up. Put in a couple of crucial challenges on his 50th Champions League appearance. 7.
PATRICE EVRA: Booked for early hand ball. Sloppy error in run-up to Olympiacos' first. 5.
TOM CLEVERLEY: Another game where the England midfielder went AWOL. Did well to last an hour before being hooked. 4.
MICHAEL CARRICK: Failed to dictate the tempo as Moyes would have liked and offered little defensive security. 5.
ASHLEY YOUNG: Puzzling choice ahead of Adnan Januzaj. Barely featured. 4.
WAYNE ROONEY: Marked out of the game. Spent as much time in his own half as he did in the opposition's. 5.
ANTONIO VALENCIA: Couple of telling tackles, but did nothing to help the United attack. 4.
ROBIN VAN PERSIE: A shadow of the player who went into the match in form. 5.
SHINJI KAGAWA on for Valencia (61mins). Provided energy but nothing else. 5.
DANNY WELBECK on for Cleverley (61mins). Exactly the same as Kagawa. 5.