It's not because they want to.
It's because they have to.
''As you know, we're getting thin here,'' Bruins coach Claude Julien said on Friday, a day after Torey Krug, in his first career NHL playoff game, scored to send the game into overtime and Boston defeated the New York Rangers 3-2 in Game 1 of their best-of-seven, second-round playoff series.
With veterans Dennis Seidenberg, Andrew Ference and Wade Redden injured, the Bruins used first-round draft pick Dougie Hamilton along with Krug and Mart Bartkowski on defense. Hamilton assisted on Krug's goal with 2:55 left in regulation, and Bartkowski played a career-high 26 minutes in the 3-2 victory over the Rangers.
''For a coach, you couldn't ask for a better situation,'' Julien said on Friday, when his team took the day off to rest up for Sunday's Game 2. ''A lot of credit goes to the coaching staff down there (in the minor leagues) that's done a great job at preparing those guys.''
Julien would not say whether any of his injured players would be able to return for the second game. If not, he'll continue to rely on his rookies. Hamilton, who made the team out of training camp and played 42 games in the lockout-shortened season, said it helps to know that he won't be yanked out of the lineup with one bad shift.
Even if it's only because the Bruins have no choice.
''For all of us, it's not just trying to belong, but getting that opportunity to get regular shifts. It helps you stay focused,'' he said. ''It makes it easier when you have that confidence that you can just stay in the game and focus on the game.''
Hamilton, the No. 9 overall pick in the 2011 draft, had five goals and 11 assists this season while averaging about 17 minutes per game. But he moved up the depth chart when injuries stripped the Bruins of three of their top six defensemen.
''We've got to remember that he's 19 years old,'' Julien said. ''He's made some unbelievable plays on some goals; we saw that early when he came in and we seemed in awe of that. Playoffs is another step and he's taken that step extremely well, to me.''
To help fill in, the Bruins called Bartkowski up from the AHL for the third time this year; he had two assists and six penalty minutes in 11 games for Boston this year. And Krug, who's played three NHL games in the past two seasons, was brought up from Providence on Tuesday after Seidenberg lasted just 37 seconds in the first-round finale over Toronto.
''What we've seen from (Krug) the few games he's played with us, he doesn't seem to be intimidated by anything, or any circumstances,'' Julien said. ''I didn't see a guy that was nervous at all. If anything, I saw a guy that was extremely confident at making the executions that he needed to make.''
The other change the Bruins made on defense was to rely even more heavily on Zdeno Chara. The 2009 Norris Trophy-winner, who averaged about 25 minutes per game in the regular season, has played about 30 minutes per game in the playoffs, including 35 minutes in Game 7 against the Maple Leafs and more than 38 in the opener of the Rangers series.
''He's in great shape, and he's got a couple of days here to recover. So I don't see that being an issue,'' Julien said. ''To be honest with you, right now we don't have a choice. You deal with it the best way you can.''
And so do the Rangers.
''With all the minutes he has, the more tired he's going to get,'' New York defenseman Steve Eminger said. ''At the end of the day, it doesn't matter if they have six veterans (on defense). We just have to put even more pressure on them and generate more offensively.''
The Rangers hope some of that offense will come from Rick Nash and Brad Richards, who have one goal between them in eight playoff games. Nash did have an assist Thursday - his third of the postseason - but has yet to find the back of the net despite taking a team-high 28 shots.
Another concern is New York's power play, which went 0 for 3 in Game 1 and has failed to convert in 14 opportunities over the last four games. The Rangers are 2 for 31 with the man advantage in the playoffs and coach John Tortorella tried to light a fire under forward Carl Hagelin, who's tied for second on the team with five points in the postseason.
"I think he's too quick," Tortorella told NHL.com when asked why Hagelin is struggling on the power-play units. "I'd like to put him out on the power play but he stinks on the power play. I can't figure it out. I can't. I love the guy. He is such an effective player, but he, as I said many times, stinks on the power play.
"But he may get an opportunity if we keep on going here."
Henrik Lundqvist, who made 45 saves in the opener, has suffered three of his four losses in the postseason in overtime.