For all the good Washington Capitals winger Brett Connolly had done Saturday night — his two goals helped his team come back twice from two-goal deficits — it was his blunder with four seconds left in the game that ultimately left the biggest mark. Connolly slashed center Aleksander Barkov in the offensive zone, putting the Florida Panthers’ impressive power play on the ice to start overtime.

Mike Hoffman decided the game 91 seconds later, handing the Capitals a 5-4 overtime loss at Capital One Arena.

“I can’t take that penalty,” Connolly said. “It’s tough. It’s an important time of the game.”

That Washington was even able to get to overtime was a tribute to the play of Connolly’s third line, which accounted for three goals. With 3:06 left in regulation, center Evgeny Kuznetsov rifled a shot from the right wall, tying the game, the third time he had flashed some late-game heroism during this homestand. Along with Saturday night’s late goal, Kuznetsov scored the game-winning tally in the last minute against the Calgary Flames on Feb. 1 and scored the overtime winner Thursday against the Colorado Avalanche. Since returning from the bye week, he has four goals and four assists in the past five games.

But even that couldn’t salvage a game in which Washington repeatedly clawed back despite its own mistakes. The Capitals had limited their penalties and buttoned up defensively over the past week, cutting down on allowing breakaways and odd-man rushes, but they fell back into some bad habits against the Panthers. The loss leaves Washington three points in back of the New York Islanders in the Metropolitan Division.

“It was one of those games where we played well enough to win but we also made enough mistakes to lose,” goaltender Braden Holtby said.

A goal from center Lars Eller in the final minute of the second period made it a one-score game going into the third, but the first seven seconds of the frame couldn’t have unfolded more disastrously for the Capitals. Nicklas Backstrom won the neutral-zone draw, but the puck skipped past defenseman Michal Kempny, who fell trying to corral it. Evgenii Dadonov was sprung on a breakaway as a result, and while Holtby saved his shot, the puck got through his shirt. Florida’s Derick Brassard then scored on the rebound, and the Panthers were up 4-2.

But for a third time in the game, the Capitals’ third line scored to make it a one-goal game. Connolly got his second goal and third point of the night; as he was falling in front of the net, left wing Andre Burakovsky passed the puck over to Connolly at the side of the net, and Connolly scored on his own rebound 6:12 into the third period.

“He had a really strong game, and it’s unfortunate that it has to end that way for him,” Coach Todd Reirden said. “To take a penalty at that time of the game — good call, bad call, whatever — that’s one we can’t take there, and they made us pay for it,”

Since the Capitals returned from their bye week at the start of the month, Reirden has emphasized cutting down on penalties with Washington leading the league in minors. In a game against Boston a week ago, he benched forwards Kuznetsov and Dmitrij Jaskin for most of the first period after they were called for stick infractions in the neutral and offensive zones. The Capitals’ penalty kill hadn’t allowed a power-play goal in the four games entering Saturday, and with Florida’s man-advantage unit ranked third in the NHL at 27.1 percent, giving it too many opportunities was ill-advised.

Winger T.J. Oshie was assessed a tripping minor in the offensive zone 10:54 into the game, and while the Panthers allowed more chances than they generated to start the power play, Frank Vatrano scored on a rebound in front one second after Florida’s man-advantage expired. Thirty-five seconds later, a point shot from defenseman Keith Yandle deflected off Oshie before bouncing past Holtby, lifting the Panthers to a sudden 2-0 lead.

The Capitals’ penalty kill then weathered a questionable elbowing call on defenseman Christian Djoos, playing in his first game since Dec. 11. He had to have left thigh surgery for compartment syndrome, and his return to the lineup made this the first game all season that Reirden has had his full roster of players available to him, with the team finally injury- and suspension-free after 55 games.

That’s especially helpful for evaluating the team with the trade deadline coming up Feb. 25. Saturday was a mixed bag.

“We were down almost the whole game,” Burakovsky said. “We’re not giving up. That’s the mentality we have on this team — we’re never giving up. We’ve been down a lot of games before and coming back, so I think there are a lot of positive things we can take from this game and just bring them into the next two.”

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