Rangers fear Kevin Thomson could miss the rest of the season with the knee injury he sustained at Kilmarnock.
The 24-year-old was stretchered off in some distress late on during Rangers' 4-0 win over Kilmarnock at Rugby Park on Sunday.
It was initially feared Thomson had suffered a serious injury and the club have conceded the prognosis does not look good for the former Hibernian man.
"Club doctor Paul Jackson accompanied the stricken player to hospital this morning where tests were carried out," a club statement said.
"The results will be available later today but Rangers are gearing themselves for bad news."
The news will be a major blow for Gers boss Walter Smith with Thomson establishing himself as a key member of his squad.