BOSTON -- When Boston Bruins defenseman Dennis Seidenberg is at his best, he's a player who punishes opponents in battles down low with his body checking and serves as a second goaltender with his shot blocking.

Seidenberg's usually at his best in the Stanley Cup Playoffs. He wrote his legend during the Bruins' run to the 2011 Stanley Cup championship as sidekick to Boston captain Zdeno Chara on the No. 1 pairing. Since then Seidenberg has been a rugged pillar of stability at the most important times for the Bruins.

In case anyone missed it, the Bruins have gotten a head start on playing playoff-caliber games because they're battling the Ottawa Senators, Florida Panthers and others to extend their postseason streak to eight consecutive years. And Seidenberg has again played a central role in the Bruins tightening up their defense and winning two in a row to take a three-point lead on the Senators for the second wild card into the playoffs from the Eastern Conference. The Bruins also lead the Panthers by four points heading into their game at TD Garden on Tuesday (7 p.m., SNE, SNO, SNW, NESN, FS-F).

Dennis Seidenberg Defense - BOS GOALS: 3 | ASST: 9 | PTS: 12

SOG: 99 | +/-: 0

Seidenberg has been playing at a higher level since every point became vital for the Bruins' survival. And he hasn't been alone.

"The whole team is kind of in that mindset right now. We have to win hockey games, we're in that position where we have to play solid hockey, try to avoid being scored on a lot," Seidenberg said over the weekend. "We try everything to try to win hockey games."

The improvement by Seidenberg and the rest of Boston's defense corps couldn't come at a better time. Defenseman Dougie Hamilton left the Bruins' lineup with an undisclosed injury during a game against the Panthers on March 21. Hamilton hasn't played since and there's no timetable for his return. Hamilton, who hadn't missed a game before this current injury, is first on the Bruins in power-play points (15) and first among Bruins defensemen in shot attempts relative percentage (SAT Rel). Hamilton also ranks third in ice time (21:20) and he was tied for second on the Bruins in overall points (42) at the time of the injury.

Since Hamilton was injured, Seidenberg and Chara have each led the Bruins in ice time twice. After giving up five goals to the Tampa Bay Lightning in their first game without Hamilton, the Bruins have allowed six goals in their past three, including games against NHL powers in the Anaheim Ducks and New York Rangers. The Bruins even survived goaltender Tuukka Rask leaving early in the second period with a migraine against the Rangers.

There's a formula in place that allows the Bruins to survive injuries on defense. It was evident when the Bruins lost Seidenberg and Andrew Ference but were able to reach the Stanley Cup Final in 2013. It showed last season when the Bruins won the Presidents' Trophy without Seidenberg and McQuaid.

The Bruins finished third in goals allowed per game two of the past three seasons. They rank 11th this season.

"Being aware of your surroundings," Seidenberg said about the key to Boston's success on defense. "Playing with layers in your own zone. And just playing as a five-man unit. It just comes down to that and just closing on opposing players and playing solid defensively. It's always the same, but if we get scored on a lot that's what we have to go back to. Go back to basics."

Although Seidenberg still ranks last among Bruins defensemen in SAT Rel (-5.7), he's last among Bruins defensemen in offensive zone start percentage, according to war-on-ice.com. Plus Seidenberg's season-long stats include the first half of the season, when he was struggling to find his form after missing all but 34 games last season because of a serious knee injury. The only Bruins defensemen to play every game this season, he leads the team in blocked shots with 136.

Seidenberg has earned the trust of coach Claude Julien at this crucial point of the season, and so have other defensemen who have been asked to make up for Hamilton's absence. Torey Krug has ranked second in ice time twice since the Bruins lost Hamilton. Krug, who is 5-foot-9 and has 37 points this season, has been working on becoming more reliable in his own end. Sometimes his size disadvantage gets in the way, and his ice time was cut against the heavy Ducks on March 26. But against the speedy Rangers he played almost as much as Chara, as the Bruins were able to divvy up their ice time more evenly with a three-goal lead for most of the third period.

Krug's speed, positioning and heart make him an attractive option to play in the Bruins' top four against the right matchups. And even if the matchups don't appear to be in his favor, he savors the opportunity to prove people wrong.

"I am [up for the challenge] because at this point in the season, I want it more than other guys," Krug said. "So you know sometimes matchups do call for things like that, but you've got to call on the guys that are getting the job done and it's something that I take a lot of pride in, especially this time of year."

Credit for the Bruins' ability to solider on without Hamilton has been shared by all the defensemen. Chara has regained his form as one of the best all-around defensemen in the League after struggling to shake off the rust from a 19-game injury absence that ended in early December. McQuaid has averaged more than 20 minutes per game in the past four games. He teamed with Chara to keep Ducks stars Ryan Getzlaf and Corey Perry off the score sheet until Anaheim scored an extra-attacker goal with 39 seconds remaining in regulation. Rookie Zach Trotman has come up and held his own, including during shifts against opposition top lines aside Chara. And Matt Bartkowski has made the most of his limited minutes by not getting caught out of position in the defensive zone and pushing the pace with the puck on his stick.

With 91 man games lost to injury to players on their back end (including Kevan Miller, who's out for the season, and David Warsofsky, who's now in the American Hockey League), the Bruins have learned how to fill in the gaps. They not only know how to expand their individual games but play together when the pairs are being shuffled.

"Yeah … at this point of the year it's about making sure we get the job done," Krug said. "It's not about playing certain guys. It's about playing the guy that's doing the job. And if we take that mentality moving forward, then guys are going to step up and play bigger roles and they're going to put the guys on the ice that are playing well."

With six games remaining in the regular season, the Bruins might have to qualify for the playoffs for Hamilton to have time to return. At this rate, though, he doesn't have to rush back.