It was the unforced error the Capitals absolutely didn’t need in the middle of the third period Sunday night while trying to protect a two-goal lead against the Philadelphia Flyers.

Troy Brouwer held up Flyers captain Claude Giroux in the offensive zone and went to the penalty box 12 minutes 32 seconds into the third.

“I was just coming around the net I just tried to get a little body positioning on him,” Brouwer said. “I thought he leaned into me a little bit but I looked at the replay, my stick was in his stomach. They’re going to call that every day.”

Only 16 seconds into the ensuing power play, Giroux fired a snap shot from the left circle to make it 4-3 and spark the Flyers’ comeback.

“Probably in hindsight Brouw would want that play back; they had nothing going behind their net. But it happens,” Coach Adam Oates said. “We let them score too quick. You can’t score in [16 seconds]. That gave them a lot of life and then here they come, and we hung on fine till the last 10 seconds.”

While it took a goal from Kimmo Timonen with 9.5 seconds remaining in regulation to tie it and another from Ruslan Fedotenko to win it 5-4 in overtime, that penalty allowed Philadelphia to change the mood of the game.

“It’s a matter of doing the right things at the right time. That penalty killed us, we’ve talked about it all year and it can’t happen,” Mike Green said. “Whether it was a bad call or whatever that’s not the point. It just can’t happen at that time in the game.”

Brouwer took responsibility for the fact that his untimely penalty helped undo the Capitals. In a season where penalties have sabotaged Washington repeatedly, Brouwer said he should have known better.

“I got to take some onus because they gave us a 5-on-3, they gave us a four-minute power play, they gave us another power play right after we just scored two goals on our PP,” Brouwer said. “We know they’re going to call one against us whether it’s warranted whether it’s not. You know it’s going to come around. It’s just careless on my part.”