from David Shoalts of the Globe and Mail,

Mats Sundin has a torn labrum, which is the soft tissue surrounding the joint in his hip, according to a National Hockey League source.
Surgery is one of the treatment options, but it is not required as long as he is in no discomfort. A medical source said surgeons will not recommend surgery as long as there is no pain and that the Toronto Maple Leafs captain can play with the injury.

continued