Pittsburgh Penguins star Sidney Crosby will miss Game 4 with a concussion.

"Sid has been diagnosed with a concussion," Penguins head coach Mike Sullivan told reporters. "He will be out for tomorrow's game. We will evaluate him from there."

Crosby suffered the concussion in the first period of the Washington Capitals' Game 3 overtime win, when he was cross-checked by Capitals defenceman Matt Niskanen as he was cutting across the net.

Niskanen will not be disciplined for the hit.

Sullivan said Crosby is upbeat after the injury. "He's very upbeat and positive. We're very optimistic and hopeful we'll have him back in a timely fashion."

Sullivan also told reporters Conor Sheary has been diagnosed with a concussion as well.

Crosby has four goals and seven assists through eight games this postseason.

The Penguins lead the Capitals 2-1 in their second round series.