PITTSBURGH -- Penguins coach Mike Sullivan is unavailable for Thursday night's game against the Philadelphia Flyers after being placed in the NHL's COVID-19 protocol.

The team made the announcement a few hours before the Penguins were scheduled to take on the Flyers. Assistant coach Todd Reirden will fill in for Sullivan.

The Penguins have been grappling with a COVID-19 outbreak since training camp opened. Eight players have entered the protocol since mid-September, including captain Sidney Crosby and defensemen Marcus Pettersson, Brian Dumoulin and Chad Ruhwedel this week. All will be unavailable to face Philadelphia.

Sullivan said Wednesday that Crosby and Pettersson were symptomatic and that Ruhwedel was asymptomatic.

Forwards Zach Aston-Reese, Jeff Carter and Jake Guentzel tested positive for COVID-19 since training camp opened but have since returned. Defenseman Kris Letang, placed in the protocol on Oct. 23, skated with his teammates on Wednesday.