NEW YORK -- So little is normal about 2020. In the minutes leading up to Game 2 of a doubleheader Friday at Yankee Stadium, a hype video played from the scoreboard in center field -- not a Yankees hype video, as typically occurs in the Bronx, but a Mets highlight reel that regularly airs before games at Citi Field.

It was a nod to the fact that the Mets, not the Yankees, were the designated home team for a game originally ticketed for Queens, before positive COVID-19 tests forced the teams to reschedule. And it prefaced something even stranger: Seven innings later, wearing a gray Mets road jersey, Amed Rosario hit the first walk-off homer by a visiting team in Yankee Stadium history.

It was the first walk-off home run by a visiting player since Ed McKean hit one for the St. Louis Perfectos at the Cleveland Spiders in 1899, and the first walk-off of any kind by a visiting player since the Phillies accomplished the feat at Robison Field in St. Louis in 1906, according to Elias Sports Bureau.

The historic hit gave the Mets a 4-3 win and a doubleheader sweep after they won the first game, 6-4.

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“When I first hit the ball, to be honest, I was so focused on that at-bat that I forgot we were the home team and that was the end of the game,” Rosario said through an interpreter. “And then as I’m rounding the bases, I see the players coming out of the dugout and I’m saying, ‘Whoa, like we just won the game right here.’ It was just exciting to be able to celebrate with them at that moment.”

“I think [Aroldis] Chapman didn’t even know, really,” Mets left fielder Dominic Smith added. “I think he was asking for another ball after the pitch. It goes to show just how weird this season has been.”

By the time Rosario reached home plate, he (and everyone else) was well aware of what he had accomplished. Trailing due to a three-run rally off David Peterson in the third inning, the Mets clawed back within one run on a Brandon Nimmo RBI double in the fifth, then put the tying run on base when Jeff McNeil opened the seventh with an eight-pitch walk. Pinch-runner Billy Hamilton immediately stole second base, placing the tying run in scoring position in the seven-inning game.

With that setup, Rosario reminded himself to let Chapman’s upper-90s fastballs travel deep enough into the strike zone so that he could punch one to the opposite field. Instead, Chapman threw two consecutive sliders, allowing Rosario to pull the second of them over the left-field fence for a game-winning homer.

Well aware of Major League Baseball’s social distance protocols, the Mets spilled out of their dugout, jumped, whooped and hollered, but stayed unusually distant from Rosario during the celebration.

“We’re just super happy for each other,” Smith said. “So when we have those big spots and big moments, it’s hard to hold those emotions back.”

If any Met needed that sort of hit, it was Rosario, who slumped deeply in mid-August amid calls for rookie Andrés Giménez to receive more playing time. Rosario entered Friday’s play batting .202 with an identical on-base percentage -- a fact that disturbed Mets officials enough to meet with him earlier this month for a discussion about his plate approach. Change came slowly for the Mets’ starting shortstop, but it arrived in a significant way against Chapman to send the Yankees to a seventh straight loss.

Although the Yankees were the home team for record-keeping purposes, the Mets had that distinction in practical terms. They batted last for Game 2 of the doubleheader -- a fact lost on only some of those in attendance.

As the Mets came to bat in the bottom of the seventh, Smith -- who had hit a go-ahead homer in the Mets’ Game 1 victory and an RBI single in the first inning of Game 2 -- walked up and down the length of the dugout saying, “Let’s walk them off! Let’s walk them off!” In the on-deck circle at the moment, Rosario could not have heard his teammate’s pleas. But everyone in the stadium heard the Mets as they congratulated Rosario afterward -- including those in the home dugout.

“I personally sat there and watched the entire celebration,” Yankees 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.”

On the opposite side of the field were contrasting emotions from players who celebrated and laughed, then bused back to their proper borough following the Mets’ first walk-off homer in their 124-game history against the Yankees.

The moment was undoubtedly unusual. It was distinctly 2020. And yet as Mets manager Luis Rojas put it, “There wasn’t anything strange in the excitement that we had when it happened.”