David Moyes admitted he was stunned by the inept display of his players as Manchester United were left on the brink of an early Champions League exit by Greek side Olympiacos.

Goals from Alejandro Dominguez and Arsenal loanee Joel Campbell gave Olympiacos a 2-0 lead at the halfway point of their Champions League last-16 tie against United.

"That's the worst we have played in Europe," the United manager said. "It was a really poor performance. We never really got going from the start and we didn't deserve anything because of the way we played.

"We never really got to grips with things and to a man you could hardly pick anybody out. We just didn't perform.

"We came into the game in good form and a good mindset but it just didn't show. I am just surprised. I didn't see that level of performance coming. I just didn't see it."

"We're not out of tie by all means, but it's not ideal" - Michael Carrick

Given that Moyes's men are 11 points adrift of the top four, winning the Champions League was seen as their best way back into the competition.

But after such a woeful performance in Athens, the odds are firmly stacked against the reigning Premier League champions making the quarter-finals.

Olympiacos goalkeeper Roberto did not have a save to make all match as Wayne Rooney and his team-mates failed to live up to their pre-match bravado.

It was United's manager who took the blame for the manner of the defeat, though.

"I take responsibility," Moyes said. "It is my time and I will always front it up. We didn't play well. We have to play better."

Although the raucous home support in the sold-out Karaisakis Stadium helped Olympiacos, the Greek champions also showed far more skill and composure on the ball.

United will have to win by three clear goals in the second leg on 19 March to make it through to the quarter-finals, but Moyes has not given up hope just yet.

"The one good thing is that there is still a second game to come," the Scot said. "We will do everything we can possibly do to reverse the 2-0 defeat."

Midfielder Michael Carrick admitted the Greek side were in "a great position".

"It's hugely disappointing but we feel like we're still in with a chance going back to Old Trafford," he told Sky Sports 2.

"Obviously it's not going to be easy. We've lost a game we came here hoping to win and haven't done that.

"We're not out of tie by all means, but it's not ideal."

Asked what went wrong, Carrick added: "I'm not sure. We had good possession in the first half. We had control of the game without penetrating their line, but at same time they weren't causing us any problems.

Robin van Persie missed a glorious late chance to snatch an away goal, but Carrick did not want to apportion blame.

"You can't blame Robin; he's created his chance and nearly scored," he said. "As players we have to stand up and take it on the chin.

"That's the business we're in. You take the good times and the bad times. We have to keep trying.

"You're looking for me to blame someone. As players we haven't been getting good results and as a club that's everyone involved. That's how we are judged."

However, Carrick was roundly criticised by former United skipper Roy Keane, who said of Carrick’s verdict: “That just reflected United's performance tonight: flat, with no urgency.”