DeSmith had not started in the NHL since March 14, 2019. Evan Rodrigues, Colton Sceviour and Marcus Pettersson scored for the Penguins (1-2-0), who won for the first time this season after being outscored 11-5 in their first two games against the Philadelphia Flyers.
"The only thing I was focused on was getting a win," said DeSmith, who came in to make 12 saves after Tristan Jarry allowed three goals on six shots in a 5-2 loss to Philadelphia on Friday. "First period they got two on me. Was glad I could battle back."
Alex Ovechkin had a goal and an assist, and Ilya Samsonov made 24 saves for Washington (2-0-1), which will play Pittsburgh again here Tuesday.
The goal was Ovechkin's first of the season and 707th in the NHL, one from tying Mike Gartner for seventh on the NHL goals list.
"It's the third game, you know, after months of time off without hockey," Ovechkin said. "It's the third game and we played against a really good team. … Have to kind of wake up and know exactly what you have to do."