Chelsea boss Andre Villas-Boas has admitted that Brazilian midfielder Ramires could be out for a month with a knee injury.

The 24-year-old was forced off in the club's 1-0 FA Cup win over Queens Park Rangers on Saturday, with Villas-Boas suggesting medial ligament damage.

"It looks like a medial knee ligament injury. Not so bad in terms of knee injuries but he'll have the MRI scan tomorrow and we'll know the full extent and I think hopefully he is going to avoid an operation," Villas-Boas told Goal.com.

"We have to know the extent of the ligament injury and eventually with the treatment and results we have been having medically, we could be looking at a four week period. We have to look at the extent of the injury. Maybe more, hopefully not."

Chelsea return to domestic action away to Swansea on Tuesday evening.