Rangers fear Kevin Thomson's season is over after the midfielder suffered a knee injury during Sunday's 4-0 win at Kilmarnock.
The former Hibernian player was carried off after badly twisting his knee and has undergone hospital checks.
The results are expected on Monday afternoon but the club's official website reported that "it looks as though the midfielder's season is over".
Thomson's knee buckled under the weight of Kilmarnock striker David Fernandez as the pair tangled towards the end of the Clydesdale Bank Premier League clash.
The fear is Thomson, who has grown in influence this season in the absence of Barry Ferguson, has suffered cruciate ligament damage.
A report on www.rangersfc.co.uk claims it looks unlikely he will play again this season.
"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 (Monday) but Rangers are gearing themselves for bad news."
Thomson suffered a cruciate ligament injury while playing for Hibs as a teenager in May 2004 and was out of first-team action for 11 months.
The 24-year-old made his Scotland debut in the goalless draw with Northern Ireland in August and has recently produced his best football since his £2million move from Easter Road in January 2007.
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