Washington Capitals left wing Carl Hagelin (62) crashes into Islanders...

Washington Capitals left wing Carl Hagelin (62) crashes into Islanders goaltender Semyon Varlamov (40) during the third period of Game 4 in Toronto, on Tuesday, Aug. 18, 2020.  Credit: AP/Nathan Denette

The Islanders still are in control of their first-round playoff series against the Capitals, but to avoid losing it, they need to get control of themselves.

That was evident after Game 4 went shockingly awry on Tuesday night, as the Islanders squandered a great start with an awful last 2 ½ periods and lost, 3-2, at Scotiabank Arena in Toronto.

They still lead the series, 3-1, and will get another crack at a close-out on Thursday.

But coach Barry Trotz and has staff have a lot to talk to their players about between now and then, specifically special teams.

That means avoiding bad penalties on one hand. It also means figuring out what is wrong with their own power play, which after an 0-for-5 night is 1-for-19 for the series.

Trotz and his players correctly noted the power play looked better Tuesday than it has recently, but they also noted, as captain Anders Lee said, “That’s not enough. We have to go back and look at this and reset a little bit.”

Said Trotz, “We put it in play a lot. We had a couple of looks. We had the zone time. But we need production out of it . . . We have to find a way to find the back of the net on the power play.”

The flip side is not giving the Capitals chances on their power play, where they have one of the greatest weapons in hockey history in Alex Ovechkin.

Ovi scored the Caps’ final two goals, the first tying the game on a power play after Barzal took an unwise penalty in his own zone.

“We took unnecessary penalties,” Trotz said, “so that gave them some momentum. They got back on track and then it was a one-shot game after that.”

For the first eight minutes or so, the 2020 Islanders looked more like the early 1980s Islanders, dominating and recording 16 shot attempts to the Capitals’ one.

They led 2-0 on goals by J-G Pageau and Barzal when Capitals coach Todd Reirden called a timeout. From that point on, Washington was the better team by far.

It was a stunning turnaround for a veteran, poised Islanders team, but then, the Capitals can say the same thing, and they won a Stanley Cup only two years ago with Trotz behind their bench.

An Islanders sweep would have been humiliating for Reirden, Trotz’s former assistant and successor. But for one night, at least, he looked brilliant after chewing into his team during that fateful timeout.

In the second period, Evgeny Kuznetsov skated around the defense and the puck squirted between the pads of Islanders goalie Semyon Varlamov to make it 2-1.

Then, after Barzal’s penalty, Ovechkin tied it from his familiar spot in the left circle.

Overall in the series, the Islanders have been the better team 5-on-5, but teams do not always play 5-on-5.

If the Islanders find a way to regroup and win on Thursday, they will have plenty of things to work on as they await their next opponent. But there was no debating what is at the top of that list.

“We have to find a way to put one in the back of the net [on the power play],” Barzal said. “We knew coming into this series special teams was probably going to be the deciding factor in some games.”

That was not the only factor in the Islanders’ weird Game 4 belly flop, but it surely was a factor.

“I thought the power play was good,” Pageau said. “We put a lot of pucks on net. We had some really good chances. It just didn’t go in. But these bounces are going to change if we keep doing the right thing.”

If they do not, the Islanders could lose the control they worked so hard to assert.