"It's a blow but one of those things you have to expect during the season," Pearce told the club's website on Tuesday.

"Vass is at home resting at the minute and we hope that the injury will not require surgery."

Former English international Vassell damaged his medial ligament during his side's 1-0 win over Arsenal in the Premiership.

City are ninth in the Premiership table with four points out of three matches.