Grabovski suffered the injury during Thursday night's win against the Predators. "I'm sure he's going to be out a while," Head coach Jack Capuano said of Grabovski.
Kael Mouillierat has been recalled to fill in during his absence.
Mouillierat, 27, leads all Sound Tigers in goals (18) and points (40) through 51 games this season. He will make his NHL debut in Washington D.C. today against the Capitals.