NEW YORK -- It doesn’t get much more 2020 than this: the Yankees were walked off in the seventh inning at Yankee Stadium.

Aroldis Chapman surrendered a pinch-hit two-run homer to Amed Rosario as the Mets handed the Yankees a 4-3 defeat, whooping it up at home plate to celebrate a sweep of Friday’s Subway Series doubleheader in the Bronx.

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“I personally sat there and watched the entire celebration,” outfielder Clint Frazier said. “I didn't expect it and I don't think a lot of us expected it with the guy that we had on the mound there and his success rate, but it's not fun.”

Appearing for the first time since Aug. 17 and the second time this season, Chapman issued a leadoff walk to Jeff McNeil, and pinch-runner Billy Hamilton stole second base despite being picked off. Rosario then parked Chapman’s 2-0 slider into the left-field seats, extending the Yanks’ losing streak to seven games.

Yankees manager Aaron Boone said that he believes Chapman’s earlier stint on the COVID-19 injured list and his lack of save opportunities played a role in his ineffective outing.

“It's not ideal,” Boone said. “We've been really trying to get him in. We've been close a couple times. With his season starting a little bit slow and now not getting regular work, hopefully we can start getting in that position more often and things will get a little more regular for him.”

The circumstances made for a strange scene; according to the Mets’ Dominic Smith, Chapman asked home-plate umpire David Rackley for another baseball, not realizing the game was over. Even Rosario didn’t realize the homer was a walk-off until he rounded second base, spotting his teammates spilling from the dugout.

“It just goes to show how weird this season has been,” Smith said.

Despite dressing in their pinstripes -- all players wore No. 42 as Major League Baseball celebrated Jackie Robinson Day -- the Yankees batted first as the “road” team. It was considered a makeup of Aug. 21, when a three-game series at Citi Field was postponed following positive COVID-19 tests among the Mets.

It was the second loss of the day charged to the Yankees’ bullpen, as Chad Green served up three sixth-inning homers in a 6-4 defeat in the first game.

Pete Alonso mashed a game-tying three-run shot into Monument Park before Dominic Smith and Jake Marisnick went back-to-back off Green, who has seen his ERA jump from 0.71 to 3.68 in two appearances.

“We feel like we've had a couple games that have just gotten taken from us right at the last second,” Frazier said.

In Friday’s nightcap, the Yankees scored their runs in the third inning. Facing starter David Peterson, Erik Kratz and Aaron Hicks connected for run-scoring hits before Gary Sánchez worked a bases-loaded walk.

Taking the mound in a quasi-opener role, Jonathan Loaisiga limited the Mets to Smith’s first-inning RBI single over three frames before the right-hander handed off to the bullpen.

Adam Ottavino, Nick Nelson and Luis Cessa combined to limit the Mets to one run over the next three innings. Brandon Nimmo’s fifth-inning RBI double off the rookie Nelson brought the Mets within one run, setting up Chapman’s stumble in the final frame.

“Some good things are happening,” Boone said. “Another good job by Lo, Otto and Nelson, getting it to Cessa to get through the middle of their order and get the ball to Chappy. We’ve just got to start finishing some games off now.”

The Yankees and Mets are scheduled to play three more games this weekend, including another doubleheader on Sunday.

“It's definitely a tough stretch -- as tough as I can ever remember,” Ottavino said. “These things come. They happen. Luckily right now, there's still a lot of baseball left. We'll try to peak when it matters.”