Rangers boss Ally McCoist was left worried after Steven Naismith was stretchered off during their 2-0 win against Aberdeen at Ibrox.
The midfielder was taken off in the first half with a knee injury after a tackle by Rob Milson.
The 25-year-old suffered a similar-looking injury in 2008 which sidelined him for eight months.
"The signs aren't good, but we won't know until we get a scan and a full diagnosis," said McCoist.
"I would have to say it probably isn't looking good at the moment as he says he feels the same pain and numbness as he did when he did it the first time.
"It's strange because I thought our team played some great stuff in the second half and thoroughly deserved their victory, but there is no doubt the shine has been taken off the result by Steven's injury."
The Scotland international signed from Kilmarnock in 2007 for around £2m.
