BOSTON — For three full periods of scoreless hockey, the Washington Capitals found themselves heavily outshot and often trapped in their own end, fending off waves of attacks from the defending Stanley Cup champion Boston Bruins and relying on perfection from rookie netminder Braden Holtby. It was a dangerous and unsustainable trend that proved costly when the contest drifted past regulation.

One minute 18 seconds into overtime at TD Garden on Thursday night, Chris Kelly fired a shot past Holtby’s outstretched glove to give Boston a 1-0 win in Game 1 of this Eastern Conference quarterfinal series. Given the number of chances the Bruins manufactured through the first 61 minutes of play, it was a testament to Holtby that they hadn’t cashed in sooner.

For 22-year-old Holtby, the goal — which appeared to have been tipped by Dennis Wideman — was an unfortunate end to a strong 29-save showing in his Stanley Cup playoff debut. He was ultimately outdueled by the reigning Conn Smythe and Vezina Trophy winner Tim Thomas, who was tested far less and finished with 17 stops.

“I think he played a hell of a game,” Capitals captain Alex Ovechkin said of Holtby, whose teammates rushed over in a show of support after Boston captured the victory. “Most of the time he kept us in the game and I think he was nervous, but after the first shot you could see he was calm and he was on his roll.”

Holtby was tougher on himself, but the consensus among his teammates and Coach Dale Hunter was that the youngster had nothing to be displeased with.

“I felt all right,” Holtby said. “Later on in the game I felt like there were some things I needed to be better at. I got a little sloppy with some things and those are the things I’ll need to make improvements on for the next game. But mainly, I wasn’t there for the boys in overtime and I’ll definitely be better for that.”

After months of talking about playoff hockey, the Capitals kicked off the real thing in front of a raucous, hostile crowd and against a rabid Boston roster that introduced itself with glass-rattling hits, followed by more hits, with a few additional hits for good measure.

Holtby appeared to fight the puck at times early on, giving up prime rebounds, but the Saskatchewan native’s confidence grew with each shot he faced.

Weathering the early physical onslaught yielded a power play for Washington when David Krejci received a minor penalty for boarding after crunching Wideman in the corner. The start of the playoffs didn’t offer a magic cure-all to the Capitals’ struggles on the man advantage, though.

Washington went 2 for 24 on the power play to close out the regular season and its opportunity of the playoffs yielded the same woeful results. The Capitals recorded one shot on goal — from 58 feet away — during the two-minute span, which they largely spent chasing Boston’s clearing attempts.

Luckily for the visitors, the Bruins’ power play wouldn’t find success, either, despite four opportunities.

Washington withstood Boston’s man advantage by limiting most of the shots to the outside, and when they did fire the puck it rarely reached Holtby. From the beginning of the contest it was clear the Capitals intended to block as many shots as possible. That was most apparent while they were short-handed, as players dove in front of chances and scrambled to turn into a point blast rather than away from it.