Manchester United are waiting anxiously to discover how seriously their striker Robin van Persie was injured in the 3-0 Champions League victory over Olympiakos at Old Trafford on Wednesday.

David Moyes, the manager, is expected to know by Friday whether the Dutch centre-forward will miss any games. It was Van Persie's hat-trick that ensured the Greek champions' 2-0 lead from the last-16 first leg in Athens was overturned.

The Dutchman suffered the problem when he was hit from behind in the last minute by the centre-back, Kostas Manolas, and collapsed on the turf clutching the back of his left knee.

While Van Persie had to be taken off on a stretcher Moyes later downplayed the problem, stating the forward had taken a knee in the back of his leg.

Given Van Persie's three goals took him to 14 in 23 United outings to make him the club's top scorer during the current campaign, Moyes will not want to lose his services.

On Saturday United travel to West Ham United, hoping to build on the win over Olympiakos that put the club in Friday's draw for the Champions League quarter-finals. They then host Manchester City in the 167th derby on Tuesday evening.

With Moyes believing that Van Persie was not too seriously hurt the manager will hope to have him return for the meeting with Manuel Pellegrini's side at the latest.

Van Persie's treble was his third for the club and the first by a United player in the Champions League in five years, following Michael Owen's hat-trick against Wolfsburg in 2009.

After a virtually injury-free season last year, Van Persie has again been cursed by setbacks this season as he was for most of his Arsenal career.

On United's summer tour Van Persie suffered a muscle injury in Japan, issues with his toes and groin once the season started, and a problem in mid-December that put him on the sidelines for six weeks.