Rangers say Steve Simonsen's condition has improved, the goalkeeper having been taken to hospital after colliding with a post against St Johnstone.
But manager Ally McCoist says the 35-year-old is doubtful for Saturday's Scottish Cup tie away to Dumbarton.
"Steve's as well as we could have hoped for," he said. "The scan showed positive results.
"He clearly had a big swelling on the left-hand side of his head, which thankfully has gone down a little bit."
Simonsen's fellow Englishman, Lee Robinson, is on stand-by to start against the Sons after coming on as a substitute during a 1-0 win over the Saints on Tuesday that took Rangers into the League Cup semi-finals.
It would mean a first Rangers start for Robinson despite the 28-year-old having spent five years at Ibrox before his present, second spell with the Glasgow club.
He also came off the bench as a replacement for Ronald Waterreus against Hearts in May 2006.
Robinson, who had loan spells from Rangers with Morton and St Johnstone, went on to play for Kilmarnock, Queen of the South, Ostersunds and Raith Rovers before rejoining the Ibrox club on a season-long deal after first-choice Cammy Bell was injured in August.
"He's a confident lad and, more importantly, he's a very good goalkeeper," said McCoist. "We've got faith in him to do a job for us and we're happy with him."