WASHINGTON — Kevin Plawecki said he was told around the sixth inning that he might pitch in Sunday’s Mets-Nationals game. Given that he’s a catcher and hadn’t pitched since he was 14, that was a bit of a surprise.

Plawecki was called on in the seventh with the Mets trailing by 14 runs. He threw a perfect inning before allowing three home runs in the eighth inning of the Nationals’ 23-5 victory.

Plawecki, who said all of his 32 pitches were fastballs, allowed four runs on home runs by Bryce Harper, Adam Lind and Anthony Rendon. But he was the only Met who smiled after the game.

“Every pitch, I was trying to be in a good fielder’s position just in case there was something hit right back at me,” Plawecki said. “Just trying to throw strikes and pump the zone.”

Duda has setback

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The Mets had hoped Lucas Duda (hyperextended elbow) could return to the lineup Monday night in Atlanta, but he couldn’t fully extend his left arm Saturday after playing Friday night for Class A St. Lucie in his first rehab game. Duda hasn’t played since.

Extra bases

Jose Reyes started at shortstop Sunday and hit second in place of the resting Asdrubal Cabrera. He extended his hitting streak to six games by going 1-for-5, a triple. He also made his fifth error . . . Curtis Granderson (.128) went 0-for-3 and is in a 1-for-28 slump. He was double-switched out of the game in the fifth . . . The two walks (one intentional) that Noah Syndergaard allowed in the first inning were his first this season . . . The 23 runs allowed were the second-most given up by the Mets (the Phillies scored 26 on June 11, 1985) . . . Nationals centerfielder Adam Eaton tore a ligament in his left knee Friday and his season likely is over, the team confirmed. Eaton stepped awkwardly on first base while beating out a hit in the ninth. He was hitting .297 with two homers and 13 RBIs.