It has been a summer of boredom, a summer devoid of moves or headlines or much of anything, really, for the Bruins. They lost Jarome Iginla and Shawn Thornton in the first hours of free agency, and if not for the signing of some restricted free agents, a Bruins fan could have been forgiven for wondering whether general manager Peter Chiarelli spent his summer fishing. But now? Now something has to be done. The Bruins stand to enter training camp with nine NHL-caliber defensemen, as Chiarelli repeatedly has stated. And while they are without the right-shot winger they could use, they have a surplus of centers. That could get a player wondering. Adam McQuaid and Chris Kelly are coming off injuries, with McQuaid having suffered through a quad injury and ankle surgery and Kelly undergoing offseason surgery to repair a herniated disk. They have, at times, been crucial players for the Bruins. But their positions are a bit more precarious entering this season. By the time the Bruins were beating the Red Wings and losing to the Canadiens in the postseason, McQuaid was a mere memory in Boston. He managed to play just 30 games in an injury-ravaged season that appeared to be yet more bad luck for a player who has seen too much of it. He returns to a crowded blue line: Zdeno Chara, Dougie Hamilton, Dennis Seidenberg, Torey Krug (as soon as the team manages to sign him), and Johnny Boychuk (as long as he isn’t traded) all will be playing. But they also have Kevan Miller and Matt Bartkowski and David Warsofsky.