Ramires will be out of action for the best part of a month.
The Brazil midfielder injured his medial ligament in the right knee during the Blues' 1-0 over west london rivals QPR yesterday in the FA Cup.
It took five minutes for Ramires to be carried off the Loftus Road pitch and many feared his season would be over.
But Chelsea confirmed this afternoon that following an MRI scan, medics have assessed the injury and he will be out of action for three to four weeks.