BUFFALO, N.Y. (AP) -Brian Pothier scored during a two-man advantage in overtime to lift the Washington Capitals to a 4-3 victory over the Buffalo Sabres on Thursday night in the preseason opener for both.

Buffalo, which had not been assessed a penalty until 39 seconds remained in regulation, incurred two in a span of 25 seconds to set up the overtime power play. Pothier fired a slap shot from the center point past Buffalo goalie Jhonas Enroth.

"Eventually you get an opportunity and you win," Washington coach Bruce Boudreau said.

Alexandre Giroux, Mike Knuble and Jay Beagle scored for Washington. Semyon Varlamov played the entire game in goal for the Capitals and made 20 saves.

"Varly was pretty outstanding in the first two periods," Boudreau said. "There were a lot of good efforts. The defensive veterans had a good game."

Buffalo coach Lindy Ruff agreed about the Capitals' goaltending.

"Varlamov was the story in the first period," Ruff said. "We could have ran away with the game, but he made four or five really good saves when we had 2-on-1s and outnumbered situations."

Jason Pominville, Clarke MacArthur, and Tim Kennedy scored third-period goals for Buffalo. Patrick Lalime started in goal for the Sabres and stopped six of seven shots in just over 33 minutes. Enroth made 21 saves.

Pominville scored 2:16 into the final period after failing to connect on two good chances during power plays in the second. MacArthur gave Buffalo a 2-1 lead, deflecting a shot at 6:12.

"I liked the effort, but our decision-making wasn't very good," Ruff said.

Giroux, a 28-year-old who scored 60 goals for the AHL Hershey Bears last season, gave Washington a 1-0 lead 8 1/2 minutes into the game, tapping in a loose puck in the goal mouth.

Giroux is looking to make an NHL roster after playing only 22 games in the league over the previous three seasons. His 60-goal season was his fifth straight of 30 or more in the AHL.

"He finds openings," Boudreau said of Giroux. "You have to give him an opportunity to see if he can do it here. He finds ways to score."