PITTSBURGH -- The scene brought back jarring memories. Sidney Crosby woozily making his way off the ice after taking a brutal hit from a member of the Washington Capitals. His brain foggy. His immediate future uncertain.

The sight of their captain slowly heading to the dressing room on Monday night following a violent cross-check to the jaw from Washington defenceman Matt Niskanen left his teammates shaken.

The diagnosis came the next morning: Crosby is sidelined indefinitely with yet another concussion.

For goaltender Marc-Andre Fleury, Crosby's nomadic two-year recovery from a concussion sustained after taking a shoulder to the head by Capitals forward David Steckel in 2011 remains fresh.

It's why Fleury's concern as the defending Stanley Cup champions prepared for Wednesday's Game 4 of their increasingly caustic Eastern Conference semifinal against the Capitals wasn't so much on how Pittsburgh will survive without its most indispensable player, but Crosby's general well-being.

"It's a tough moment for sure," Fleury said. "You know, you care a lot about him ... We've been friends for a long time. I know he's always devoted to the team. He's always working hard out there. Hoping he feels better soon and see him smile again."

Crosby spent part of Tuesday at the team's training facility being evaluated. Barely 12 hours removed from a hit that sent a jolt across the league and provided a stark reminder of Crosby's concussion history, the game's best player tried to focus on pushing forward instead of looking back.

"He's very upbeat and he's very positive," Pittsburgh coach Mike Sullivan said. "We're very optimistic and we're hopeful that we'll get him back in a timely fashion."

Just not in time to try and help the Penguins build on the 2-1 lead they take into Game 4 (7:30 p.m. ET, NBCSN). Sullivan declined to speculate on Crosby's availability beyond Game 4.

"The nature of these things is they're all very different," Sullivan said. "Sometimes they come around quickly. Other times they don't."

Crosby would know. He missed the second half of the 2010-11 season and most of 2011-12 following the hit by Steckel. He sat out two weeks after being diagnosed with a concussion last October, returning in time to play in 75 games and score an NHL-high 44 goals.

Pittsburgh forward Conor Sheary could also be out of the lineup on Wednesday after being diagnosed with a concussion following a collision with teammate Patric Hornqvist, leaving the Penguins in a familiar position: trying to win without some of the bold-faced names that helped them capture the franchise's fourth Stanley Cup last June. Goaltender Matt Murray and defenceman Kris Letang are already out, absences Crosby's brilliance has helped the Penguins overcome.

This, however, is something different.

"You can't replace (Crosby) but I think we've shown that through the season whenever the guy's not there, other guys have to step up," Fleury said. "And we're lucky to have depth on our team. I think we have enough to win games."

Niskanen received a five-minute major and a game misconduct after his stick caught his former teammate across the jaw. He will play after the league decided against holding a hearing to review the incident.

Washington coach Barry Trotz called it "the right decision" while stressing the cross-check was "a hockey play."

Fleury said the Penguins can't get caught up in trying to retaliate, though Washington expects Pittsburgh to ramp up the physical play going forward.

"It should be nasty," Washington forward Jay Beagle said. "It's the playoffs. That's the way we like to play. That's the way they like to play. Hard hits. Going after each other."

Even without Crosby, the Penguins won't lack for star power. As if sensing a change in the dynamic of the series, Pittsburgh forward Evgeni Malkin went back out for a brief postgame skate on Monday night and was one of a handful of regulars who showed up for an optional skate on Tuesday.

Malkin won the Hart Trophy in 2012, the same season in which Crosby was limited to just 22 games. The Russian has a way of raising his game with Crosby out. The Penguins will need him to do it again if they want to survive without Crosby.

"He does things with the puck like no one else," Hornqvist said. "He looks like he's playing loose. He's a hell of a player. We're looking forward to tomorrow and get the win."

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Ducks at Oilers, Edmonton leads 2-1 (10 p.m. ET, NBCSN)

A Stanley Cup Final featuring Crosby and Edmonton star Connor McDavid is a tantalizing prospect, but Crosby's long-term status was unclear after suffering a concussion Monday, though McDavid declined to join the chatter surrounding the injury.

"I saw the play. It happened so fast, I don't have too much of an opinion on it," McDavid said. "You never want to see someone get hurt obviously, especially at this time of the year."

McDavid led the NHL during his second season, posting 100 points on 30 goals and 70 assists to earn his first Hart Trophy nomination, joining Crosby and Columbus goaltender Sergei Bobrovsky.

The going has been a bit slower for McDavid in his playoff debut. He has three goals and three assists in nine games for the Oilers, who are in control of their second-round series during their first post-season appearance in more than a decade.

Anaheim managed to get back into the series with a 6-3 victory in Game 3, though McDavid's spectacular goal during a brief Edmonton rally showcased the skills that have the 20-year-old poised ready to pick up where Wayne Gretzky and Mark Messier left off nearly 30 years ago. McDavid picks Gretzky's mind frequently.

"Now especially, more than ever, I've had to rely on him and talk to him about certain things," McDavid said. "Just going through this whole thing for the first time."

The Ducks will likely be without forward Patrick Eaves, who was limited in the third period of Game 3 with a lower-body injury. Defenceman Kevin Bieska is also likely to miss a third straight game.

The Canadian Press contributed to this report.