David Moyes is confident that the knee injury suffered by Robin van Persie against Olympiakos is not too serious.

The Dutch striker's hat-trick gave Manchester United the 3-0 win they needed to progress to the quarter-finals of the Champions League.

Van Persie was carried off on a stretcher in the dying minutes of the match having fallen awkwardly after a tackle by Giannis Maniatis.

"I don't think he is too bad," the Manchester United manager said. "He has got a knock just behind his knee. We will assess it and we will know more on Friday.

"He has got a knock in the back of his knee but hopefully it is not too bad."

Van Persie scored a penalty and then converted Wayne Rooney's cross before rounding off the win with a 20-yard free-kick in the second half.

"To score a hat-trick in Champions League football is a big thing," Moyes said.

"I think there are only certain players in the world capable of it, and Robin van Persie is one of them.

"He gets his penalty kick, he scored a great free-kick and Wayne did brilliantly well for him for the second goal.