Sidney Crosby is back on the ice.

The Pittsburgh Penguins captain, who missed Wednesday's Game 4 against the Washington Capitals due to a concussion, took part in an optional, no-contact practice Thursday.

It is an off day for the Penguins but Crosby was on the ice with a few other players in full gear. — Shawn McKenzie (@ShawnMcKenzieSN) May 4, 2017

"Sid skated this morning (and) is in the process of rehabbing," Penguins head coach Mike Sullivan said later. "We'll leave it at that. It's a day-to-day process."

Crosby suffered the concussion after a cross-check to the head delivered by Matt Niskanen early in Game 3. He missed six games at the beginning of the regular season due to the same injury.

Last time Crosby got concussion diagnosis, skated on his own next day. He kept skating and undergoing testing. Came back two weeks later. — Nick Cotsonika (@cotsonika) May 4, 2017

Game 5 of the series, which the Penguins lead 3-1, is scheduled for Saturday in Washington.