"He has ruptured his cruciate knee ligaments so he's going to be out for at least six months," Bruce told Sky Sports News. "It's a tragedy."
But Bruce is certain Campbell will make a full recovery from the injury he sustained on Saturday, and prove his worth to the club.
"Fraizer will be back. He's a larger-than-life character," said Bruce.
"He was just starting to show what he was about. But make no mistake he'll be back and he'll be firing again."