Sidney Crosby faces an indefinite layoff after suffering the latest in a series of concussions during Pittsburgh's playoff defeat to the Washington Capitals, Penguins coach Mike Sullivan confirmed on Tuesday.

Canadian icon Crosby was flattened by a brutal cross-check to the head from Washington defenseman Matt Niskanen in Monday's 3-2 loss to the Capitals.

Sullivan said Tuesday Crosby had suffered a fresh concussion and would miss Game 4 of the best-of-seven Eastern Conference series, which Pittsburgh lead 2-1.

"Sid has been diagnosed with a concussion. He will be out for tomorrow's game. We will evaluate him from there," Sullivan said.

Sullivan said Crosby was bullish about returning however to play some further part in the series.

"He's very upbeat and positive. We're very optimistic and hopeful we'll have him back in a timely fashion," he said.

Crosby has a history with concussions after a collision in the 2011 Winter Classic outdoor game set off a long recovery that shortened two seasons for him.

The Canadian star was diagnosed with a third documented concussion last October, forcing him to miss the start of the NHL season.

The latest injury will revive concerns about the long-term health of one of ice hockey's biggest stars.

Meanwhile, Capitals player Niskanen, who was given a five-minute major and a game misconduct for the collision with Crosby, denied attempting to intentionally hurt the Penguins ace. 

"I've seen the replay," Niskanen said. "In super slow-mo, it looks really bad. I caught him high. He's coming across trying to score. As he's doing that, he's getting lower and lower, and when it's happening that fast, you know, my stick and his head collided. I wasn't extending trying to hit him in the head. It happened quickly," he added.

"I wasn't even trying to cross check him with a serious amount of force. A collision was going to happen there in the crease. When the play first starts, I think my stick's at about his arm level probably, right about where the numbers are on the side of his jersey. 

"And because he's trying to make a play, he's getting lower and lower because he's getting pressured, trying to score, so the collision happened there."

source: AFP