The elation of the Bruins’ improbable Game 7 comeback victory was tempered with the loss of Dennis Seidenberg, the shutdown defenseman who suffered a leg injury on the first shift of the game in a collision with the Toronto Maple Leafs’ Matt Frattin. Coach Claude Julien said that it could be known today whether the injury would be short term or long term. He came out for the second period and skated gingerly, then returned quickly to the bench and was unable to play again. Seidenberg was walking on his own after the 5-4 overtime win that concluded the Eastern Conference quarterfinal series, but with a noticeable limp. “He wanted to (continue), but when he couldn’t, it was better to take (him) out than to make it worse,” Julien said. “It wouldn’t have helped us, plus, it would have made his injury probably even worse.” The injury made an already trying situation downright dire. The B’s were already without two veteran defensemen in Andrew Ference and Wade Redden (undisclosed ailments) and had two rookie replacements in the lineup in Matt Bartkowski and Dougie Hamilton. Bartkowski’s first NHL goal was also the B’s first goal of the game, and he wound up playing 24:51, while Hamilton played 21:08. Meanwhile, captain Zdeno Chara played 35:46 on defense and Johnny Boychuk pitched in with 28:30. “You have to find a way to give credit to those two young guys on the back end — Hamilton and obviously Bartkowski,” Julien said. “Bartkowski was moving the puck and carrying it so well tonight, and he scored a big goal for us. I saw Dougie Hamilton get more and more comfortable as the game went on as far as carrying the puck and making plays. You talk about people coming in, well we were minus three real good veterans in our back end, so that’s half your core, and those guys come in and do a heck of a job.