Manchester United striker Robin van Persie will miss up to six weeks with a left knee injury, ruling the Netherlands striker out of both legs of a Champions League quarterfinal against Bayern Munich and potentially six Premier League games.
It is a major blow to United's hopes of winning the Champions League, which realistically is the club's only route back into Europe's top competition next season.
Following a second scan on the injury on Friday, United said Van Persie has a "sprained knee which will keep him out for around 4-6 weeks."
He appears to be in no danger of missing the World Cup finals in Brazil beginning in mid-June — the worst-case scenario according to United's diagnosis is that Van Persie is out until the start of May, leaving him available for the last two or three league games in United's season.
Van Persie, who has scored 23 goals in 29 games for club and country this season, was carried off on a stretcher after hurting his knee in a challenge from behind toward the end of Wednesday's 3-0 victory over Olympiakos, in which he scored a hat trick to send his team into the last eight.
United is seventh in the Premier League after its humiliating 3-0 loss to Liverpool last weekend, 12 points adrift of fourth-place Manchester City having played two more games.
A finish in the top six would qualify United for next season's Europa League, and sixth-place Everton is three points ahead with a game in hand.
It will be a second significant spell on the sidelines for Van Persie this season — he played just two games across 2 1/2 months over the turn of the year because of groin then thigh problems.
The news punctures some of the optimism that has spread through Old Trafford after the victory over Olympiakos, which came just as the pressure was beginning to build on manager David Moyes.
Moyes has Danny Welbeck and Javier Hernandez as alternatives up front to partner Wayne Rooney. Otherwise, Moyes could decide to play Rooney as his main striker and move Juan Mata, signed in January for a record fee of 37.1 million pounds ($61.2 million US), into his favoured No. 10 role just in behind.
Mata has played out wide in recent games, to little effect.