VANCOUVER — The Washington Capitals have allowed at least one power-play goal in seven of their past eight games. So what is Coach Barry Trotz seeing from his struggling penalty kill unit?

“Can’t kill anything,” he said Thursday night after the Capitals lost to the Vancouver Canucks, 6-2.

“Just a lot of extra pucks, a lot of failed clears,” Trotz said. “When you’re spending a lot of time in your zone and they’re putting pucks there, they’re going to find the back of the net. That’s what’s happening. It starts a little bit with failed clears and, you know, we’ve just got to be better back there.”

Vancouver entered Thursday night’s game with one of the worst power plays in the NHL, scoring on just 10 percent of its opportunities. But the Canucks feasted on Washington’s penalty kill, scoring three goals on six power plays. Through 10 games, the Capitals entered Friday’s NHL action with the third-worst shorthanded unit in the league with a 73.3 percent penalty kill percentage, and the team has allowed six power-play goals in its past three games.

“I don’t know. I wish I had an answer for you,” forward Jay Beagle said. “I really don’t know. We’re going to go through the tape, obviously, and try to figure it out. Structure-wise, I think it’s little reads. I think we can do better disrupting their breakout. …

“I think there’s other things that happened, but if I had to pinpoint one thing, I think I can do a better job at the neutral zone and make sure they’re not entering our zone so easy and with full possession and time.”

The unit had personnel changes after the offseason departures of forward Daniel Winnik and defenseman Karl Alzner, both of whom logged heavy shorthanded minutes last season. It also doesn’t help that defenseman Matt Niskanen is out of the lineup with a left hand injury; he’s typically one of the first defensemen over the boards on the penalty kill.

With Niskanen out, blue-liners Brooks Orpik, John Carlson and Dmitry Orlov have the heaviest shorthanded burden, and they’re also the ones playing the most at even strength, making for some tired legs in both situations. It hasn’t helped that the Capitals have taken 46 minor penalties through 10 games, tied for fifth-most in the league.

Alzner’s presence seems to be especially missed as so many of the power-play goals seem to be coming directly in front of the net, where Alzner would typically clear opposing players out of the crease. Winnik was Beagle’s partner on the top unit, and Washington has tried both Devante Smith-Pelly and Alex Chiasson in that role this season.

“There’s a lot of dirty goals — shots and pucks kind of bouncing the wrong way for us and right way for them,” Beagle said. “But you don’t want to blame it on that. I think we’ve just got to watch the film. We’ve got to look at it and figure this thing out.”

Washington allowed the fewest goals in the league last season, and its strong penalty kill was part of the reason. With an 83.8 percentage, the Capitals’ shorthanded unit ranked seventh in the NHL last season. The year before that, it was the No. 2 penalty kill with an 85.2 percent success rate.

But the Capitals had the same struggles at this time last year, too. As Washington began its Western Canada swing, its penalty kill had allowed five goals in the first six games. Trotz made some personnel adjustments, namely moving forward T.J. Oshie to the top unit with Beagle for a short stretch of games, and the group quickly rebounded to be one of the league’s best by the end of the year.

The fix may not be so simple this time. The forward corps is already depleted because of injuries, and Oshie already is averaging 19:41 per game, so adding to his ice time may not be feasible. With the Capitals having lost four of their past five games, they need to find a solution soon.

“It’s pretty restricted right now, so we’ll probably stay with the group we have,” Trotz said. “We’ve just got to work with them. It’s a process. We’ve got some young guys back there. We’ve got some older guys playing heavy minutes, too. It all has an effect.”