This was the situation: Orioles and Yankees tied at 4 in the top of the 10th inning. Aroldis Chapman, the Yankees’ sixth pitcher, had relieved Bryan Mitchell after he tossed a scoreless ninth.

But wait. Mitchell remained in the game at first base, playing the position, he said, for the first time since 2009, when he was a high school senior in Reids ville, North Carolina. The Yankees were out of fresh relievers, Joe Girardi said, so the idea was to have Chapman pitch the 10th and bring Mitchell back if the Yankees could not win Sunday’s game in the bottom of the inning.

The last time a Yankees pitcher played in the field was on Aug. 18, 1983, when Ron Guidry was the centerfielder in the final inning of the resumption of the famous pine tar game against the Royals.

Before the buzz around the unorthodox move by Girardi could subside, Mitchell had to negotiate a pop-up from leadoff batter Welington Castillo. It was a routine pop down the line, in foul territory, but Mitchell dropped the ball, which fell in front of him. He was given an error for prolonging the at-bat of Castillo, who singled but did not score.

Mitchell gave up three runs in the 11th in the 7-4 loss, but all anyone wanted to talk about was his adventurous debut at first base.

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According to Elias, he’s the first major-leaguer to pitch, play first and pitch again in a game since the Brewers’ Chuck Crim in 1989.

Pitching coach Larry Rothschild had told Mitchell to grab a first baseman’s glove (Greg Bird’s, as it turned out) after the ninth. Mitchell knew what Girardi had in mind.

“I really didn’t want to use Tommy Layne too much,’’ Girardi said. “Adam [Warren], I wasn’t going to use, so it was the only way to use Chappy, I felt, to give us a chance in the bottom of the inning to win the game, and then I would go back to Mitchell. So it was the only way I could do it.’’

Mitchell was ready, and he didn’t have to wait long to be tested.

“I guess I should have expected the first one to find me,’’ he said of Castillo’s pop-up. “I know I can catch a fly ball. I guess I just went back too far and the ball had a lot of spin. I thought I was going to catch it but it just never got there.’’

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Mitchell got another chance. After Chapman struck out Trey Mancini, Jonathan Schoop popped up a ball off first base, in foul territory. Mitchell made a two-handed catch to loud cheers, and the fans chanted his name.

“It was pretty funny,’’ he said of the reaction. “It was nice. I was laughing to myself a little bit.’’

Mitchell’s teammates were concerned and amused when they saw him at first base.

“I would be nervous as hell if that was me out there,’’ said Dellin Betances, who pitched a scoreless eighth. “You don’t want to see him drop that first one . . . It was just a weird situation to be in, to be honest with you.’’

Warren added, “I could just imagine what it felt like out there. If a ground ball was hit to him, we just don’t practice that.’’

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With Erik Boland