The backup thrust into a starting role while two-time Stanley Cup winner Matt Murray recovers from a lower-body injury and shaky play stopped a career-high 48 shots as Pittsburgh fended off a third-period Boston rally to slip by the Bruins 5-3 on Friday night.

DeSmith improved to 7-2-1 in his last 10 starts, keeping his cool even after the Bruins erased a two-goal deficit in the third period by scoring twice in 54 seconds. Jake Guentzel restored Pittsburgh’s lead by tipping home Kris Letang’s point shot with 9:13 to go, and DeSmith did the rest.

“It’s always fun, though, when you’re getting peppered as long as you come out on the right side of things,” DeSmith said. “It was a little (chaotic) there at the end but glad we pulled it out.”

The Penguins appeared to be firmly in control after Zach Aston-Reese’s short-handed goal — Pittsburgh’s first down a man in 57 games — with 58 seconds to go in the second period made it 3-1.

Boston’s Chris Wagner and David Krejci drew the Bruins even when they beat DeSmith less than a minute apart in the third. But the Penguins executed perfectly on a faceoff in the Boston zone, with Sidney Crosby winning the draw and then sending the puck back to Letang. He shot it and Guentzel extended his stick to get a piece of it. The puck slid by Jaroslav Halak for Guentzel’s 13th of the season.

“I know he’s going to shoot it,” Guentzel said. “I just put my stick there and hit it. We run that (play) in practice. Sid kind of gave the nod so we knew it was coming. Obviously a great play by Sid.”

Brandon Carlo scored for the first time in 115 games for Boston and Halak stopped 24 shots but the Bruins had trouble with DeSmith, who has filled in capably with Murray spending most of the first two months of the season dealing with injuries or a serious dip in form.

The team activated Murray on Wednesday but coach Mike Sullivan has chosen to stick with DeSmith, though Murray is likely to make his first start since Nov. 17 on Saturday night when the Kings visit. DeSmith insists he won’t change his approach now that he’s engaged in a full-on competition battle for playing time.

“I think when I get a game, I go out there, try to win, try to play my best,” DeSmith said. “(Just) keep working hard in practice, doing all the same things. That’s the way to keep having success is to not change anything once you get a hold of it.”

The Bruins dominated for long stretches thanks in part to sloppy play by the Penguins, but DeSmith managed to keep Pittsburgh in it.

“He’s a good goalie, but I thought our scoring chances weren’t A scoring chances, especially in the first period,” Krejci said. “But that’s how it goes sometimes.”

DeSmith’s flashiest stop came in the first. He was sliding to his right when Brad Marchand picked up a bouncing puck and moved to DeSmith’s left. The goaltender reached back with his glove and plucked a shot out of midair to keep the game scoreless.

“I just kind of fell over and stuck something over there and thankfully it went in my glove,” DeSmith said. “That was not technique.”

Derek Grant gave the Penguins the lead shortly after DeSmith’s save on Marchand. Phil Kessel, playing in his 277th consecutive game with the Penguins — the fourth-longest streak in franchise history — and 723rd straight overall, doubled Pittsburgh’s advantage 1:56 into the second period.

The Bruins responded by pressing Smith, who eventually relented when Carlo fired a laser from the top of the right circle 11:53 into the second for just the seventh goal of his career and first since March 4, 2017, against New Jersey.

“It had been a long while,” Carlo said. “But I feel like with the way that I’m starting to put the puck to the net a little bit more, the opportunities were coming for me to shoot the puck, tonight especially.”

Though Boston eventually pulled even, Pittsburgh still ended up pulling away, with Aston-Reese putting in an empty-netter with six seconds left to ice it.

NOTES: Letang exited late in the third period favoring his left leg and did not return. … If Kessel stays healthy, he could break Craig Adams’ club record of 319 straight games played near the end of the regular season. … The Bruins were 0 for 2 on the power play. The Penguins were 0 for 1.

UP NEXT

Bruins: Welcome the Sabres on Sunday. Boston took the first meeting 4-0 in Buffalo on Oct. 4.

Penguins: Host the Los Angeles Kings on Saturday night.