Robin van Persie
van Persie was stretchered off in the 90th minute after suffering a blow to the knee.

Manchester United manager David Moyes is hopeful Robin van Persie's knee injury picked up against Olympiakos will not be deemed serious.

Van Persie scored a hat-trick to help United overturn a 2-0 deficit from the first leg against the Greek champions and book their place in the Champions League last eight.

But injury to the Dutchman overshadowed an otherwise perfect evening for Moyes, who saw the pressure over his position eased by United's crushing win, but the Scot is confident of a quick recovery.

"I don't think he's too bad," said Moyes. "He's got a knock just behind his knee and we'll assess it and we'll know more in the morning. He's got a knee in the back of his knee and hopefully it's not too bad.

Moyes added: "To score a hat-trick in the Champions League is a big thing. There are only certain players in the world who are capable of it and Robin van Persie is one of them.

"He scores a penalty kick, a great free-kick and took Wayne's ball down brilliantly for the second goal so it's great that he got a hat-trick because he's a top player and I think he showed that today."

Amid Van Persie scoring three times to send United through, Ryan Giggs rolled back the years to star throughout at Old Trafford.

Giggs, who had been linked with a fall-out with Moyes in the lead-up to the game, hadn't made a start for United since January but was parachuted in to reignite the club's European challenge.

"His two passes which made two of the goals were fantastic but his all-round play was really good," the United boss added. "He defies his age. He's a great player and everyone envy's him who has been at Manchester United.

"He's 40 years old and I need to be looking to the future," explained Moyes. "I have been trying to give everyone opportunities to play but I just felt that tactically I need him to play a certain role for me. He carried it out perfectly as well as assisting in the goals."