On Monday, in the town where he played most of his NHL games, Chris Kelly suffered the most significant injury of his career. The Bruins center broke his left tibia at 0:42 of the second period of the Bruins’ 3-2 shootout win over the Senators at Ottawa’s Scotiabank Place. Kelly is out indefinitely. The severity of the break is unknown. The Bruins have not said whether he will require surgery. Kelly, 32, was hurt when he collided with former Senators teammate Chris Neil. The Ottawa bruiser banged his left knee into Kelly’s leg. Neil said it was an accident, a sentiment shared by Bruins coach Claude Julien. Kelly traveled with the Bruins to Pittsburgh Monday; at the time, the team had not determined the nature of the injury because of swelling.