Olympiakos Piraeus made it fifth time lucky on Tuesday, sweeping past an abject Manchester United team 2-0 in their Champions League last-16 first leg at the Georgios Karaiskakis Stadium.

Alejandro Dominguez opened the scoring with a clever first-half flick and Arsenal loanee Joel Campbell added a sublime second goal to leave United facing a huge task to overturn the deficit in the return match at Old Trafford next month.

"That's the worst we've played in Europe. We didn't deserve to get anything," United manager David Moyes was quoted as saying by the BBC. "I'm surprised, I didn't see that level of performance coming.

"I take responsibility, we have to play better. The players are hurting."

Defeat represented another body blow in an inauspicious season for the English Premier League title winners.

The Champions League is United's last chance of a trophy and they looked sluggish and disjointed against an inexperienced Olympiakos side who are bidding to reach the quarter-finals for only the second time in their history.

It was the first time the Greeks had beaten United in five attempts.

Moyes opted to start with two wingers, Antonio Valencia and Ashley Young, but neither made an impact in a first half in which Olympiakos displayed real energy and hunger.

After a cautious opening from both sides amid ear-splitting noise from an enthusiastic home crowd, the first chance fell to Olympiakos with Dominquez bursting through the middle on a solo run only to be denied by a last-ditch tackle from Nemanja Vidic.

Midfielder Tom Cleverley registered United's only effort of note in the first half with a 17th-minute half-volley that sailed high over the bar.

Peripheral figures

Strike pair Wayne Rooney and Robin van Persie were peripheral figures for the visitors as pot shots on goal from Giannis Maniatis and Hernan Perez lifted the home supporters.

Olympiakos, wearing red and white jerseys, red shorts and socks, broke the deadlock seven minutes before halftime with a clever piece of improvisation from Argentine forward Dominguez.

Patrice Evra's half-hearted clearance from a corner landed at the feet of Maniatis 25 metres out and his tame, low shot was expertly diverted past keeper David De Gea by Dominguez's flick.

United, the European champions in 1968, 1999 and 2008, were punished again for poor defending 10 minutes into the second half.

Campbell, who is likely to feature for Costa Rica against Group D rivals England at the World Cup in Brazil in June, did the damage.

He picked up possession 25 metres out, jinked past midfielder Michael Carrick and sent a curling left-foot shot around defender Rio Ferdinand and into the bottom corner of the net.

Moyes sent on Danny Welbeck and Shinji Kagawa for Valencia and Cleverley but it was more a change in attitude than personnel that was required from United.

Dutch striker Van Persie summed up his team's night with five minutes to go. He received the ball 12 metres out and turned inside a defender before blazing a right-foot shot way over the bar.

"We had good possession in the first half and were controlling the game without really penetrating and causing them any problems," said Carrick. "But at the same time they weren't causing us any problems and the goals came from nothing.

"We didn't start the second half very well, we were a bit sloppy really, and they scored the second goal which put us on the back foot."

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