Manager Billy Davies is struggling to keep hold of the 24 year old and has already rejected a bid of £1 million from Celtic.
“I can can confirm that Kelvin has got a shin injury which has forced him to miss the last couple of games,” he told the club’s official website.
“It would be difficult for him to go on strike when he’s carrying an injury because he can’t play anyway.”
A club spokesman added: “We can confirm that Kelvin has an injury.
“He took part during the pre-season trip to Portugal but since he returned he has picked up a shin injury and that is the reason he has not played.”