According to Daily Faceoff's Frank Seravalli, there's concern that the 27 year old could have torn his ACL, in which case, his timeline for return could be pushed back considerably.
Coming off a pretty nice season with the Toronto Maple Leafs last year scoring a career high 21 goals and 32 points. This was his chance to take on a bigger offensive role, and his season may be over before it's begun, you never know with these types of injuries.