Lightning forward Ryan Callahan likely will miss the start of next season because of surgery on his right shoulder.Callahan had surgery and will be out five months, the team said Thursday. That time line means he would be out until November. The season typically starts the first week of October.Callahan dislocated the shoulder Dec. 14 and missed three weeks. He reinjured it in March and missed five games.The shoulder also kept him out of two games in the first-round playoff series against the Devils. He returned, however, and had a solid postseason with two goals and an assist and a plus-1 rating in 15 games while usually matching up against the other team's top scorers.This is the third shoulder surgery in four years for Callahan, 33, who just finished the fourth year of a six-year deal with the Lightning. Playing mostly a defensive role, he had five goals and 13 assists in 67 games this season.That wasn't the only news coming out of the Lightning on Thursday. A week after being eliminated in the Eastern Conference final, the Lightning shook up its coaching staff, letting go of associate coach Rick Bowness and mutually agreeing to part ways with assistant Brad Lauer.Bowness, 63, is one of the most respected coaches in the NHL, but the news doesn't come as a surprise. Bowness coached the Lightning's defense and penalty kill for the past five seasons. But Tampa Bay struggled defensively at times this season. It allowed 230 goals (13th out of 31 teams) and an average 32.7 shots per game, which was 23rd in the NHL. It was 27th in penalty killing."After giving it lots of thought and discussing it with (head coach Jon Cooper), we felt we needed to make some changes to improve our hockey club," general manager Steve Yzerman said. "And we're hopeful that some new voices, some new ideas will improve our team.''Yzerman said he does not have a specific replacement in mind but hopes to begin putting together a list of candidates in the coming days."We have some people in mind that we'd like to talk to, but I think it's fair to say we're kind of starting with kind an open list,'' Yzerman said.With changes on the coaching staff, Yzerman was asked if he ever considered making a head coaching change."No,'' Yzerman said, "that has never been a consideration.''Look for assistant coach Todd Richards, a former Blue Jackets and Wild head coach who joined the Lightning staff in June of 2016, to take on a greater role now that Bowness is gone. Meantime, goalie coach Frantz Jean is expected to return next season.