(CNN) -- Manchester United are sweating on the fitness of Rio Ferdinand after the central defender picked up a rib injury in the dying moments of their Champions League semifinal against Arsenal on Wednesday.
A dazed Ferdinand is helped from the field after damaging his ribs against Arsenal on Wednesday.
The England international had to be helped from the field and appeared to be dazed after the late clash in the United penalty area as he tried to clear a Cesc Fabregas free-kick.
Nicklas Bendtner got his head to the ball in Arsenal's best attacking moment of the match, but a clearly winded Ferdinand was left clutching his chest after the ball was cleared.
"Rio got a crack right on the ribs and we hope there's nothing broken," manager Alex Ferguson told their official Web site.
"If you get a rib injury, you could be out for two to three weeks maybe. We just have to wait for the (hospital) results obviously."
Northern Ireland international Jonny Evans came on for Ferdinand for the final few moments and he is set to deputize for Saturday's Premier League game against Middlesbrough.
United are set to shuffle their squad for the match at the Riverside ahead of the return against Arsenal on Tuesday. With the holders having a slender 1-0 lead, Ferdinand's absence for the second leg and in the title run-in could be crucial.
United have been hard-hit by injuries to established defenders this season, but Wes Brown, who can play in central defense or full-back, is fit again after a long-term injury and may be included in the squad for the Middlesbrough match.