This first-round series was supposed to be too much for the Washington Capitals to handle. A matchup against the deep, physical defending Stanley Cup champions would render them inadequate, pundits said. Experience would win out in the head-to-head battle between their rookie netminder and the reigning Vezina and Conn Smythe winner in the other cage.

But, as it turns out, last year’s trophies don’t guarantee playoff series the next spring.

With a 2-1 overtime victory in Game 7 on Wednesday night at TD Garden, the Capitals dispatched the Boston Bruins and punched their ticket to the Eastern Conference semifinals for the third time in the past four years.

Fourth-line winger Joel Ward scored the game winner 2 minutes 57 seconds into overtime by driving to the net and swatting a rebound past Tim Thomas, who was preoccupied by Mike Knuble’s presence on top of him in the crease. It was a clutch time for Ward to score his first tally with a goaltender in the net since Jan. 7 at San Jose.

“It’s not about relief. We didn’t feel we had the pressure on us tonight. We’ve played these guys tough for six games going into tonight. We knew we could beat them,” Matt Hendricks, who recorded Washington’s first goal, said of the emotion he felt when Ward’s shot crossed the goal line. “We had the confidence playing in this building, we had the confidence that we were going to come and do the job we had to do.”

Ward, Hendricks and the rest of the grinders on Washington’s third and fourth lines led the charge, helping tip the balance in the final chapter of this taut series. It marked the first time in NHL history that each game of a seven-game series was decided by one goal.

“To have seven one-goal games and four overtime games, this certainly was the best, most competitive series since I’ve owned the team,” Capitals owner Ted Leonsis said in the packed visitors dressing room at TD Garden. “That [goal] was beautiful. That wasn’t pretty, that was beautiful. I think winning any way you can is what playoff hockey is about. It’s always one mistake, one turnover.”

Rookie netminder Braden Holtby finished with 31 saves, outdueling the veteran Thomas (25 saves) one final time and, combined with the Capitals’ stingy defense, rendering one of the regular season’s most potent offenses flummoxed.

Knocking the Bruins out of the postseason also gave Dale Hunter a victory in his first series as an NHL head coach. The usually stoic bench boss didn’t hesitate to express his happiness at the milestone.

“It’s awesome,” Hunter said. “By being an ex-player I know what it takes, what the players are going through over there; they get to blocking shots and taking big hits, they’re sacrificing. So for players, I think it’s one of those things when you win big games like this it’s because they sacrificed, and they did tonight and through the whole series.”

For a game with so much emotion, it was a tentative start. Hendricks scored his first career playoff goal to give the Capitals a 1-0 lead 11:23 into the first. For the sixth time this series, the team that took the initial lead would go on to win.

Boston forward Milan Lucic overskated the puck on the half wall, allowing Jason Chimera to move it along to John Carlson at the point. The Capitals defenseman threw the puck on net as several bodies passed through the crease, where Hendricks redirected the shot past Thomas.

As they have throughout much of the series, the Bruins would outshoot the Capitals (32-27). But something about Washington’s simple game and dedication to minimizing mistakes while focusing on supporting Holtby seemed to throw the defending champions askew.

“I think everybody’s made commitment, is buying into it,” Nicklas Backstrom said. “And we’re playing good hockey, I think. That’s the way you’ve got to play to be successful, I think, in the playoffs.”

Tyler Seguin evened the score at 1 with 14:27 gone in the second period when he fought off Karl Alzner and Carlson to swat a loose puck over the goal line. A shot by Johnny Boychuck had squeaked between Holtby’s arm and body, leaving the puck unprotected in the blue paint behind the netminder.

While the Bruins would have additional chances in the third period – and a quality scoring chance early at the start of overtime – they would be the team undone by one last bounce that didn’t go its way.

On the play that led to the game-winner, Knuble blocked a shot by Benoit Pouliot that sent the rush back in the Capitals’ favor. The veteran right wing carried the puck all the way to the net for a shot and as he crashed into Thomas, Ward found the rebound and made sure it made it into the back of the cage.

Where the Capitals can go from here — and even their next opponent, which could be the Rangers, Devils or Flyers, depending on the outcomes of two Game 7s on Thursday — remains to be determined, but knocking out Boston is a powerful opening statement.

“I think that’s with any team — get past the first, you’re on a high and you never know what’s going to happen,” Holtby said. “It’s a lot of work. There’s a lot of work to be had. This is just the start of it. We’re not going to let it soak in too much. We have a goal and it’s three more rounds from now.”