Steven Naismith has had a scan on the knee he injured in Rangers' 2-1 victory over Aberdeen on Saturday.
Naismith suffered suspected cruciate ligament damage and expects to find out the results of the examination on Tuesday.
The Scotland international twisted his knee when stretching to make a challenge on Aberdeen midfielder Rob Milson.
The former Kilmarnock player played on following the incident but soon crumpled to the ground when receiving the ball with no other players near him.
He was carried from the pitch on a stretcher and replaced by Kyle Lafferty.
Naismith endured a nine-month absence from first-team action after suffering cruciate ligament damage in his other knee in April 2008.
Rangers released a statement on their official website confirming Naismith had seen a consultant with a full prognosis to follow, but admitted they feared the worst.
The statement continued: "However, the signs are that it is a serious problem and the Scotland star will be out of action for a considerable time.
"The fear is that Naismith has suffered damage to his anterior cruciate ligament in his right knee and if that is the case he will be unlikely to feature again this season.
"Naismith suffered a similar problem in his left knee in 2008 and was out for eight months."