When a team has as much success as the Bruins have had over the last couple of years, it’s not all that surprising that there hasn’t been much turnover. But sooner or later in a salary cap system, teams get hit with certain financial realities. And this offseason, the B’s have been knocked upside the head with not only the natural evolution of their payroll structure but also a declining salary cap. That led to the departures of — in some part, at least — Nathan Horton, Tyler Seguin, Rich Peverley, Andrew Ference and Anton Khudobin. The B’s core is essentially intact, but that’s a good chunk of turnover. That will mean when the Bruins reconvene for training camp in September, there will be more competition for jobs than in the last couple of years. The makeup of the third line is a big question mark, some slots and minutes on the back end will be up for grabs, and the backup goaltender — not an afterthought for a team that uses its No. 2 liberally — has not yet been determined. But in athletics, competition makes the world go round. And though this situation has been largely foisted on him, general manager Peter Chiarelli doesn’t seem to mind that he’ll be seeing a little more of it when camp opens, especially knowing what a Stanley Cup hangover can to do a team.