He has been in strong form for the Gers, even being called up to the Rangers first-team for the pre-season friendly Newcastle-Gatshead Cup competition last weekend.
But he was hit by a late challenge playing in the 4-1 friendly win over Armadale on Friday, meaning he looks set to miss the start of the season.
U21 manager John Brown said: "We are obviously concerned about the injury that Tom picked up.
"He has had an excellent pre-season and it would be a shame if he was to miss the start of the season.
"It was a bit of a late challenge from the Armadale lad, and you could see immediately that Tom was hurt. We will have to wait and see what the outcome is."