Sir Alex Ferguson is 'praying' Nemanja Vidic did not suffer a serious injury in Manchester United's 2-0 win over Roma.
Vidic was hurt after half-an-hour of the UEFA Champions League first-leg tie at Stadio Olimpico after landing awkwardly following a header.
He was taken off and replaced by John O'Shea, with the Serbian centre-half due to undergo a scan on the knee problem on Wednesday.
Ferguson is hoping it is not a serious problem, but is reluctant to suggest how long Vidic may be missing.
"I pray it is not serious, because he is such an integral part of our team," said Ferguson
"We think it might just be a nerve injury, but we can't be sure at this moment."
The United manager also praised the contribution of keeper Edwin van der Sar, who has been struggling with a groin injury of late.
He added: "He's had one or two injuries - which have given us a bit of concern - but he came through the game well.
"Edwin showed why he has 120 caps. His experience is vital.
"He made one incredible save in the second half and is a great goalkeeper."