Borna Barisic is facing a race against time to be fit for Sunday's Old Firm derby.
The left back hobbled off injured against PSV last night in Rangers' heavy Champions League play-off defeat.
The Croatian defender appeared to pull a muscle around the 50-minute mark in Eindhoven, with the game still 1-0 at that point.
He was replaced by natural right back Dujon Sterling, with Ridvan Yilmaz also on the sidelines at the moment.
The game finished 5-1 as Michael Beale's men crashed out of Champions League qualifying at the final hurdle.
They will now play in the Europa League between September and December.
Next up is the small matter of the derby against Celtic. The match will be played at Ibrox on Sunday lunchtime.
It's highly unlikely that Rangers will dip into the transfer market for another left back with just two days remaining in the window.
It's not yet known how serious Barisic's injury is yet, with Beale likely to clear this up in his pre-match press conference tomorrow.
Sterling could get the call to play in that position against Celtic, while youngster Adam Devine also has experience of filling in there.
Johnly Yfeko is another option at left back, having played there against Morton in the Viaplay Cup.
James Tavernier believes Rangers shot themselves in the foot by conceding poor goals in their Champions League defeat to PSV.
He said: "It is obviously really raw and hard to take at the moment. We knew how much it meant to the fans and the club.
"Obviously the scoreline is really disappointing. It is something that we need to move quickly on with a really important game at the weekend."
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