For 57 minutes and 6 seconds, the Washington Capitals thought their Game 7 against the New York Islanders would tick by penalty free. A bruising 100 hits were exchanged, but whistles were seemingly swallowed until John Carlson was called for roughing with less than three minutes left in the game.

“It’s never a good feeling,” Carlson said. “You never want to do that.”

“It must’ve been something pretty bad,” defenseman Brooks Orpik said with a laugh. “There’s no penalties all game and then you call one with three minutes to go. You don’t see that very often.”

Carlson skated over to the penalty box, his stomach knotted as he watched his team down a man while clinging to a one-goal lead. For the 14th time this series, the Capitals killed the power play en route to their 2-1 series-clinching win, staying perfect on the penalty kill in the postseason. Washington is the only team that hasn’t surrendered a power-play goal in the playoffs.

“It’s probably not the easiest way to finish the game,” Orpik said. “But we killed it off nonetheless.”

Said Islanders Coach Jack Capuano: “We go through the whole series and I would have never really guessed that we wouldn’t score one power-play goal in this series.”

The late man advantage was one of the few opportunities New York had on offense. The Capitals controlled possession for most of the game and allowed the Islanders just 11 shots on goal, the fewest New York posted all season and one shy of Washington’s franchise record for fewest allowed. The Capitals blocked 15 shot attempts in the third period.

The Islanders didn’t have a single shot on goal during the power play.

“Tonight was pretty easily our best game of the year,” goaltender Braden Holtby said. “We’ve played like that in spurts during games, but a full 60 minutes of that effort is a sign of a winning team.”

Holtby said the Capitals’ success while shorthanded this postseason is part luck and part shutting down New York’s entries, which caused the Islanders to force plays. In Game 4, Washington killed off three power-play opportunities in six minutes in the second period.

Carlson said that in the playoffs, power plays are “maybe a little bit overrated” because there is not as much space as in the regular season with every player trying to block every shot. But Carlson said killing off a penalty can be important for momentum. The Capitals’ highly touted power-play unit scored just twice.

“If you told us the penalty kill would be 100 percent at the beginning of the series, I would’ve doubted it would’ve been a one-goal game in Game 7,” Orpik said.

Washington was ranked 14th in the league at the end of the regular season in penalty-killing percentage with 81.2, and the Islanders scored 50 goals on power plays in the regular season, which was ninth in the league. Orpik said he saw the unit get better as the season went on. Capitals Coach Barry Trotz said “the players have bought in” by improving on penalty kills, which the coaching staff emphasized entering the postseason.

“The way it was being called, you didn’t expect a call to be made at all,” Holtby said. “I’m not sure why the last one was, but we were calm about it. We knew our jobs that had to be done and everyone stepped up and made the right plays.”