QPR say Sam Field will be out for “three to four months” with a knee injury.
West London Sport revealed on Thursday that Field, 23, had suffered the injury in training and faced a spell on the sidelines.
A scan showed medial collateral ligament damage in his left knee and Field will require surgery.
QPR’s head of medical Dr Imtiaz Ahmad told the club website: “Sam went for a scan on Thursday evening and unfortunately that revealed a tear to the medial collateral ligament in his left knee.
“As a result, he will require an operation. Procedures of this nature usually have a recovery time of approximately three-to-four months.
“Sam is obviously disappointed but is already displaying a real determination to come back stronger than ever.”
Field joined the R’s on a permanent deal this summer, having spent the second half of last season on loan from West Brom.
Meanwhile, Rangers are close to completing the signing of Stefan Johansen on a permanent deal.