PITTSBURGH, Pa. - The Pittsburgh Penguins are heading into a critical game without their workhorse star defenceman.

Kris Letang, who played upwards of 400 minutes more than the next closest Penguins defender during the regular season, was suspended one game on Tuesday for his elbow to the head of Capitals winger Marcus Johansson in Game 3 of a second-round Stanley Cup playoff series.

He'll sit out Game 4 on Wednesday evening at Pittsburgh's Consol Energy Center.

His absence to the Penguins, even for a game, can't be understated, especially since promising 21-year-old defenceman Olli Maatta seems likely to remain out with an upper body injury.

"If we lose him it's going to be a big loss," Pittsburgh winger Conor Sheary said before news of the suspension was announced.

Letang played nearly 28 minutes Monday in the Penguins' 3-2 win, a nervous victory that required a heroic 47-save effort from 21-year-old goaltender Matt Murray. A 29-year-old Montreal native, Letang was third among NHL defencemen with 67 points during the regular season and has seven points in eight playoff games this spring.

He's averaging more than 29 minutes in the post-season, nearly seven minutes more than the next closest Pittsburgh defender, 32-year-old Trevor Daley.

Letang does everything for the Penguins.

He eats up minutes against the imposing Washington top line of Alex Ovechkin, T.J. Oshie and Nicklas Backstrom, kills penalties and stands as the lone defenceman on Pittsburgh's top power-play unit.

His absence creates another vacancy on a top defensive pairing already missing Maatta, who was injured by Capitals defenceman Brooks Orpik in Game 2.

Orpik received a three-game suspension for the hit. The Capitals believed a similar punishment was owed Letang.

"It's late, it's at the head and he leaves his feet," Oshie said of the hit after Game 3. "It's up to (the league), though. Whatever they decide or what they don't decide doesn't matter to us. We're playing the same way."

Johansson didn't practice for Washington on Tuesday morning and his status for Game 4 is unclear. He returned to the game after the hit from Letang, evidently passing concussion tests in the Capitals dressing room.

With Maatta sidelined, the Penguins turned to rookie Derrick Pouliot for Game 3. The 21-year-old Weyburn, Sask., native played about 12 minutes in his first ever NHL playoff game, though saw little ice during the Capitals furious third-period comeback. Pouliot felt rusty early, better as the game wore on.

"I think I got the first one out of the way so I won't be as nervous coming into the next one," said Pouliot, who hadn't played since April 9 prior to Game 3. "I've got another level of my game. You didn't see my best (Monday) night. Hopefully I'll get better as the series goes on."

Pouliot could be joined in Game 4 by Justin Schultz, who has one career NHL playoff game under his belt, which came in Game 1 of a first round series against New York. The 25-year-old former Edmonton Oiler hasn't suited up since, not quite finding a fit after a mid-season trade to Pittsburgh.

Penguins coach Mike Sullivan described Schultz as someone who could help move the puck and be an option, potentially, on the team's power play.

His entry into the lineup would leave the Penguins with two rusty and inexperienced defencemen in Game 4 opposite one of the highest powered offences in the league. Heavier minutes are all but a certainty for Daley and 24-year-old Brian Dumoulin, among others.

A better performance is required of Pittsburgh regardless.

Even with Letang, the Penguins still surrendered 49 shots on Monday night, a substantial decline from a Game 2 in which they gave up only 24 shots.

"I think we were the better team in the first two games; I think Washington was the better team in Game 3," Sullivan said on Tuesday. "We have to make sure we understand how we have to play and what's brought us success and we've got to get back to that."

Pittsburgh leads the best of seven series 2-1.