OAKLAND, Calif. — It was a debut to forget for Greg Weissert.

The right-hander from Long Island who pitched at Fordham University was called up by the Yankees on Thursday and entered in the seventh inning of the Yankees’ 13-4 rout of the A’s.

He hit Jonah Bride with his first pitch and a balk sent Bride to second before Weissert drilled Skye Bolt with his second pitch.

After a visit from pitching coach Matt Blake, Weissert got Nick Allen to fly to center, but it was the only out he recorded, as he then walked Tony Kemp to load the bases and Vimael Machin to force in a run.

The rough outing came after Weissert, who pitched at Fordham University, replaced Nestor Cortes on the roster after Cortes was placed on the IL with a strained groin.

Weissert is part of a bullpen that’s missing Scott Effross (shoulder), Albert Abreu (elbow) and Clay Holmes (back).

He thrived at Triple-A Scranton/Wilkes-Barre this season, with 67 strikeouts in 46 innings, as well as a WHIP of 0.891 in 40 appearances.

None of the stuff he showed with SWB was on display Thursday at Oakland Coliseum.

“It’s only up from there,’’ Aaron Boone said of his message to Weissert after the ugly outing. “Things sped up on him a little bit, but it doesn’t change what we think about him,’’ Boone said. “We think he can really help us. Get that one out of the way and we’ll try to get him back out there in a different situation.”

Weissert, who said he grew up a Mets fan and had about 10 family members and friends in attendance on Thursday night at Oakland Coliseum, pitched three years at Fordham before being drafted by the Yankees in the 18th round in 2016.

The 27-year-old, who also played at Bay Shore High School, became the first Fordham player to play for the Yankees since Johnny Murphy in 1946.

Murphy, who was also a right-handed reliever, spent almost all of his 13-year career in The Bronx and was part of seven World Series-winning teams and later was general manager of the Mets. Hank Borowy spent parts of four seasons with the Yankees as a reliever from 1942-45.

Weissert’s coach at Fordham, Kevin Leighton, knows if nothing else, his former player has the mindset to succeed with the Yankees.

“He’s kind of a bulldog,’’ Leighton said by phone before heading to Oakland for Weissert’s debut. “He’s a tough kid with a ‘no fear’ type of mentality. He always wanted the ball.”

Leighton said he used Weissert as a closer as a freshman before moving him to the rotation as a sophomore and junior.

“What makes him good is he always pitched with a little bit of ego to him,’’ said Leighton, a former Seton Hall catcher. “He knows he’s pretty good and I think he pitches that way.”

Weissert has been especially impressive lately, with one earned run allowed in his last 29 ¹/₃ innings, while striking out 44 and walking seven.

“You could see he was never afraid,’’ Leighton said. “He pitches with attitude and aggressiveness. He wasn’t a showboat type of guy, but you knew when he was on the mound, he was confident. Whether he did well or struggled, he believed in his stuff and gave everything he had. That’s what I want from someone on the mound and what makes him good. I don’t know how he’ll react in Pinstripes, but he won’t be afraid of the big moment.”