BOSTON - Braden Holtby, who will likely win the 2015-16 Vezina Trophy as the NHL's top goaltender, has allowed three goals in beating the Boston Bruins five straight times over the last two seasons.

But Saturday night, with a chance to go 6-0 against the Bruins in two years, Holtby sat at the end of the Washington Capitals bench and watched backup Philipp Grubauer face Boston.

The result didn't change.

Grubauer made 33 saves, 20 of them in the second period and several with his team down two men for 1:49, and defenseman Matt Niskanen scored in overtime as the Caps reached the 100-point mark with a 2-1 victory.

"That was phenomenal. He kept us in the game," said defenseman Karl Alzner, who scored the Capitals' first goal. "They had a lot of great chances. A lot of tough kills but I feel like Gruby has been growing his game as the season has gone on.

"A little bit of pressure at the beginning of the year with being that No. 2 goalie, making the jump full time and I think every game he has gotten better and better. You feel a lot of confidence when he goes in the net right now and that's a really good sign. He's eating up pucks, just gobbling them up, so it's kind of fun to watch him be in there and feel confident and see him after the game feeling happy."

Niskanen slapped his fifth goal of the season past Tuukka Rask at 2:24 of the overtime for the Capitals (48-13-4), who lost Friday night but still haven't dropped two straight games in regulation all season.

"It was an entertaining hockey game today for sure," said Niskanen. "A little bit of everything - physicality, penalty killing, goaltending. It seemed like there was a lot more scoring chances than a 1-1 game or 2-1 game would indicate.

"Heck of a hockey game. Fun to be on top."

Alzner tied the game in the second period after Patrice Bergeron (seven shots on goal, plus a post during the two-man) scored his 26th goal of the season in the first.

Rask made 28 saves for the Bruins, who fell to 15-16-4 at home and 36-23-7 overall. Rask fell to 1-8-4 lifetime against the Capitals.

Bruins defenseman Kevan Miller suffered a shoulder injury and was sent to a hospital when he was boarded by Alexander Ovechkin in the second period. Ovechkin was hit with a major penalty but not ejected and, soon after, the Bruins wound up with a two-man advantage for 1:49 but couldn't score.

Ovechkin assisted on the first Capitals goal and has 38 points in 39 career games against the Bruins.

Asked about the hit, Ovechkin said he didn't expect any league discipline and added, "Even the referee said I get five minutes because I was heavier than him."

The Bruins saw it a bit differently, coach Claude Julien saying, "If it's somebody else, is it a game [misconduct]? You guys can answer that question yourselves."

Said Bruins captain Zdeno Chara: "I think that obviously it was from behind. You know, it's a dangerous, dangerous play. I'm just hoping that Kevan is going to be okay."

The Bruins took a 1-0 lead when Bergeron converted a nifty pass from Brad Marchand at 7:11 of the first period.

Torey Krug pounced on a rebound of a David Pastrnak shot and beat Grubauer with what would have been the defenseman's first goal in his last 40 games 3:17 into the second. The Capitals challenged, saying Loui Eriksson was offside and, on a close call, the challenge was won and the goal was taken away.

Niklas Backstrom's backhand pass was tipped home by Alzner at 13:08 of the period to tie the game, Alzner's first goal in 22 games and Backstrom's 30th point in 28 games against Boston.

NOTES: The Capitals hope to have D Matt Niskanen named to one of the remaining spots on the United States team for the World Cup of Hockey. "He's an under-the-radar top defenseman in the National Hockey League," coach Barry Trotz said Saturday. ... LW Zac Rinaldo, suspended for five games by the NHL before being sent to the minors by the Bruins, got permission to play from the NHL and was quickly suspended indefinitely pending a hearing after he hit Bridgeport's Kane Lafranchise in Rinaldo's first game on Friday night. ... The Bruins play 10 of their next 13 games on the road, while Washington opened a four-game trip on Saturday. ... The Caps, who have been giving up the first goals of games too often in recent games, and did it again Saturday night, are a plus-60 goal differential in the second and third period this season. ... The Bruins did a video happy birthday tribute to club great Milt Schmidt on his 98th birthday.