What the …?

The Seattle Mariners committed five errors — FIVE ERRORS — in the first inning Sunday in an epic breakdown that led to a 10-1 thumping by the New York Yankees.

“It was, obviously, the worst inning we’ve had all year,” Mariners manager Scott Servais said. “Embarrassing. But there’s nothing we can do about it now. We’ve got to forget about it. Move on.”

Here are the details. They’re aren’t pretty.

The Mariners had just wasted a chance to hang a crooked number on New York starter Masahiro Tanaka (10-10) when they put on a vaudeville show behind luckless Andrew Albers (2-1) at Yankee Stadium.

After Albers retired Aaron Hicks on a pop up, Starlin Castro doubled to right. Gary Sanchez followed by poking a single to left that skipped past Ben Gamel for error No. 1. Castro scored, and the error permitted Sanchez to reach second.

Aaron Judge walked before Didi Gregorius sent a pop into short left-center field. Shortstop Jean Segura called off Gamel and center fielder Guillermo Heredia before pulling up and failing to make the catch. Error No. 2. Bases loaded.

Chase Headley hit a potential double-play grounder to third base that Kyle Seager bungled on the glove-to-hand exchange for error No. 3. Everyone was safe. One run scored, the Yankees led 2-1 and still had the bases loaded with one out.

Albers struck out Todd Frazier before the inning really slipped away when Jacoby Ellsbury sliced a drive toward the left-center gap. Played cleanly, it was a two-run double, but Segura dropped the relay throw from Gamel for error No. 4, which permitted Headley to score.

Segura then rushed a belated throw to the plate that bounced past catcher Mike Zunino, which permitted Ellsbury to reach third base. Error No. 5, including error No. 3 in the inning on Segura.

Ronald Torreyes followed by beating out a grounder to third for an RBI single, which pushed the lead to 6-1, before Albers ended the inning by retiring Hicks on a fly to center.

“The snowball got rolling,” Servais said, “and we couldn’t stop it. You’ve got to make plays. Everybody knows that. We know we screwed up today. There’s nothing we can do about it now.

“We’ve got to react a good way (Monday) and get after it over in Baltimore.”

Seattle’s five errors were the most in an inning in club history. The previous major-league team to make five errors in one inning was the 1977 Chicago Cubs, according to the Elias Sports Bureau.

The Mariners played clean defense the rest of the day but still matched the season high for errors by a big-league team in one game this year. Boston made five errors Friday against Baltimore, and Milwaukee did it July 7 at Yankee Stadium.

As bad as it was, the cliche is correct: It’s only one loss. The Mariners are 66-65 and still just 1 1/2 games behind Minnesota in the race for the American League’s final wild-card berth.

The Mariners played error-free after the first inning, which means their franchise record for errors in a game remains seven — on June 25, 1978 at Milwaukee. They also scored seven runs over last three innings that day and won 10-8.

That obviously didn’t happen Sunday in the Bronx.

The Mariners scored in the first on Nelson Cruz’s run-scoring double, then missed out on a chance to do more damage. With two runners in scoring position, Tanaka struck out Seager and retired Mitch Haniger to end the threat.