West Ham midfielder Jack Collison has suffered a dislocated kneecap and is facing six to seven weeks on the sidelines.
The Wales international sustained the injury in the Hammers' stormy 1-0 success over Wigan at the JJB Stadium when he crumpled to the turf in agony 12 minutes from time.
Collison, who underwent surgery earlier this week, will now miss the forthcoming Premier League fixtures against West Brom, Blackburn, Sunderland, Tottenham and Aston Villa.
A swift recovery would give him an outside chance of being involved in the home date with Chelsea on 25th April, but it is more likely he will not return until the final month of the campaign.
The news is a further blow to Hammers boss Gianfranco Zola who has already lost Valon Behrami's services for the next six months after he ruptured cruciate knee ligaments in the victory over Manchester City.
The 20-year-old Collison has made 16 Premier League appearances this season, scoring three goals, and is regarded as one of the brightest young talents at Upton Park.
A statement on the club's official website read: "Collison underwent an arthroscopy to assess and deal with the injury on Tuesday and is recovering well."