Steven Naismith has been ruled out for the rest of the season with anterior cruciate ligament damage, Rangers have confirmed.
Naismith, 25, underwent scans on his right knee on Monday and has been told he faces eight to nine months on the sidelines.
The striker, who has netted nine goals for the Scottish champions this term, suffered the injury during Saturday's 2-1 win over Aberdeen in the SPL.
Naismith appeared to twist his knee while challenging Rob Milsom during Saturday's clash at Pittodrie. He attempted to play on but collapsed to the turf with no-one near him moments later.
The former Kilmarnock player sustained a similar injury to his left knee in 2008 and was out for eight months.
A statement from Rangers read: "Scans have confirmed Steven Naismith sustained an anterior cruciate ligament injury to his right knee during Saturday's game against Aberdeen at Pittodrie and he will sadly miss the rest of the season.
"Steven will be seen by the same surgeon who successfully treated him in 2008 and his rehabilitation programme will be 8-9 months.''
Manager Ally McCoist backed Naismith to come back from the latest injury in the same way he did last time.
He told Rangers' official website: "This is devastating news for Steven and our thoughts are with him. He was in the form of his life and it is a huge blow for him and the club that he is out for the rest of the season.
"He will get the best treatment possible in the weeks and months ahead and everyone at Rangers Football Club will support him during his rehabilitation period.
"Naisy has recovered from a serious knee injury before and he will come back again. He is a fighter and a popular member of the squad and we will all work hard to win games for him while he is out.''