Penguins defenseman Ian Cole (28) sends Washington right wing Justin Williams (14) to the ice on a hard third-period hit. (John McDonnell/The Washington Post)

With less than two minutes left in a crucial Game 4, goaltender Braden Holtby started to skate to the bench to give the Capitals an extra attacker. But with Washington fighting for an equalizer in front of the Penguins’ net, forward T.J. Oshie was called for high-sticking, putting the Capitals on the defensive again.

Video replay showed Oshie’s stick never actually made contact with Nick Bonino’s head, but the call marked the sixth offensive-zone penalty of the game, and it assured Washington’s 3-2 loss that put the Capitals in 3-1 hole against Pittsburgh in this Eastern Conference semifinal series. The Capitals’ season is one loss from being over.

“Tough time to get a penalty,” Oshie said. “That’s kind of an amateur play by me there. You’ve got to check with your feet in those big moments. I don’t think I got him that hard, but I’ve been on the other side, and the natural reaction when you get hit in the head is your head snaps back. It’s unfortunate and tough to be in that situation.”

This game was a big moment for the franchise to take a step toward getting over its second-round hump, and yet Washington fell flat. The defeat feels particularly damning considering who wasn’t on the ice. Pittsburgh’s superstar captain, Sidney Crosby, was ruled out with a concussion, as was forward Conor Sheary. With No. 1 defenseman Kris Letang and top goaltender Matt Murray already out for the series with injuries, a fully healthy Capitals team was unable to beat a depleted rival.

Nate Schmidt (88) celebrates with teammates after tying the game in the second period. (John McDonnell/The Washington Post)

The wounds were self-inflicted.

With Washington down a goal entering the second period, the most frustrating moment of the postseason arrived just 3:51 after intermission. Forward Jake Guentzel’s centering pass went off the right skate of Washington defenseman Dmitry Orlov in front of the net, and the puck caromed straight into the Capitals’ net for an own goal.

“It was just bad bounce,” Orlov said. “I don’t think if he going to like throw 20, 30, 40 pucks, I don’t think it’s going to go in. Kind of wait for that, it just bounced so hard and go in the net. Bad bounce for us.”

Washington responded with a strong push, scoring twice in 72 seconds to tie the game. Evgeny Kuznetsov scored his third goal of the series when he beat goaltender Marc-Andre Fleury with his quick release from the left faceoff circle. Defenseman Nate Schmidt then tied the game 8:33 into the period with a snap shot.

But the Capitals again cost themselves when defenseman John Carlson took an offensive-zone penalty. He went to the box for roughing, and after Washington’s penalty kill had managed to limit the Penguins’ potent power play to just one goal in its past 12 opportunities in the series, Pittsburgh defenseman Justin Schultz scored the go-ahead goal with a point shot.

Defensemen Karl Alzner, left, of the Capitals and Olli Maatta of the Penguins are on a collision course. (John McDonnell/The Washington Post)

“We had all of the momentum in the second period, and we had a defenseman go down the wall on a little bit of a cycle. He’s looking for the puck, and he runs into one of their guys,” Capitals Coach Barry Trotz said of Carlson’s penalty. “We get a penalty, and that sort of killed momentum. Some of it is self-inflicted, and some of it is just the way the refs called the game.”

The Penguins finished the second period with just four shots on goal, but while Washington was outshooting Pittsburgh 29-13, the Penguins again were ahead on the scoreboard. What few chances Pittsburgh had, it capitalized on. Of the many the Capitals had, they couldn’t collect enough. They finished with 38 shots on goal.

“It’s a little frustrating,” Oshie said. “I think we’ve got to do a better job getting to the interior. We had some golden opportunities to score goals, and for whatever reason, we didn’t put them in. Those have to go in.”

With the Capitals on a power play to start the third period, Alex Ovechkin was called for slashing, wasting the man-advantage opportunity and taking yet another offensive-zone penalty. After the game, Ovechkin was critical of his play, and Trotz said he wanted to see more from his top players.

“I didn’t play my game at all tonight,” Ovechkin said. “I think, me personally, I have to play much better.”

A lot of the intrigue entering the game was on how the Penguins would fare without Crosby. Less than six minutes into Game 3 on Monday night, Capitals defenseman Matt Niskanen cross-checked Crosby in the head, knocking him out for the rest of that game with a concussion. Niskanen was ejected for the remainder of Game 4, but the NHL decided against additional discipline, so he was back on the ice Wednesday night, booed every time he touched the puck.

Crosby is the NHL’s best player and scored a league-leading 44 goals in the regular season. Rather than physically retaliate against the Capitals in defense of Crosby, the Penguins chose to get retribution through their strong play early in the game.

With Niskanen back in the lineup, Washington dressed a lineup of 11 forwards and seven defensemen, meaning the blue line corps rotates partners. Against a speedy Pittsburgh line of center Matt Cullen and wingers Carl Hagelin and Patric Hornqvist, the Capitals had a defensive pair of Brooks Orpik and Karl Alzner on the ice. Orpik and Alzner are arguably Washington’s slowest skaters, and Hornqvist was able to split the duo before skating past them and beating Holtby on a breakaway just 4:39 into the game.

That was just the first defensive miscue for the Capitals on a night, arguably, when they beat themselves. They have put themselves in position that their next mistake could end their season.

“Now our backs are against the wall,” Trotz said. “Next game is the most important game of the year. If we don’t have the urgency that we need in that game, then we won’t earn the right to keep playing.”