Kelly is one of three Bruins forwards who will not play in Toronto due to the goings on against Pittsburgh. Shawn Thornton has been suspended pending a hearing with NHL player safety and Loui Eriksson sustained a concussion.
The news of Kelly's ankle injury, which happened on a slash by Pascal Dupuis, was first reported by TSN's Darren Dreger.
Dreger tweeted, "Bruins forward Chris Kelly suffered broken ankle from Dupuis slash last night. Quite a game."
This is the second leg injury for Kelly this calendar year. Back in March, during last year's lockout shortened season, Kelly broke his left tibia, an injury that kept him out for a month and kept him ineffective until late in the postseason.