After missing four games in NHL COVID-19 protocol, Letang wrapped a backhand around the right post for his first goal this season. The defenseman had symptoms before being cleared Monday.
Letang led all skaters with 28:54 of ice time.
"The last four days, after I got all my screenings, I tried to stay on the ice as much as I could just to get the feel back," he said. "Ten days without skating, it's a long time, so I tried to get as much as I could in the last four days. But a little tired, as expected."
Crosby did not play after he entered COVID-19 protocol Wednesday. The center has missed eight of nine games this season, including the first seven after having wrist surgery Sept. 8. Sullivan and defensemen Brian Dumoulin, Chad Ruhwedel and Marcus Pettersson are also in COVID-19 protocol. Pittsburgh assistant Todd Reirden assumed Sullivan's duties.
Tristan Jarry made 36 saves, and Jake Guentzel scored for the Penguins (4-3-2), who ended a three-game losing streak.
"There's a number of things to take from a game like that," Reirden said. "To me, going through the adversity we've gone through and being able to come out of it that way was something I pointed out with the team and was something I was really proud of how we handled it."
Scott Laughton tied it late in the third period, and Carter Hart made 33 saves for the Flyers (5-2-2), who had won three of four.
"I think it's a good point anytime you can pick it up down a goal with a couple minutes left," Laughton said. "You always want to get the extra one. I thought [Hart] played a pretty outstanding game and gave us a chance to win. He's really dialed in right now.
"I think we can do a little bit of a better job making it harder on other teams' goaltenders and throwing different things at them."