"It's unfortunate for Stevie," physio Jon Whitney told the club's official website.
"He has been training hard for the last week or so and there has been no reaction to the initial injury to his right hamstring.
"Up until Tuesday he was fit and available for selection for Saturday's game.
"However, at the very end of training we were warming down and he felt his left hamstring go.
"We've done a few tests and it seems as though he's pulled the hamstring, which could rule him out for another two weeks or so. It's a frustrating injury because all you can do is wait for it to heal."