OAKLAND, Calif. – Should they tangle in the AL wild card game, the Athletics’ lockdown bullpen had given the Yankees a close-up look at a fearsome, signature Oakland strength.

Five relievers had blanked the Yanks over the final four innings in Oakland's 6-3 Labor Day win.

Yet, the Yankees broke out a potential new bullpen weapon of their own.

“That was pretty impressive,’’ Yankees manager Aaron Boone said after Jonathan Loaisiga threw two scoreless innings, with four strikeouts. “He was dominant.’’

Loaisiga’s immediate re-entry into Yankees Universe was a smash, striking out the side in order — Khris Davis, Stephen Piscotty and Matt Olson — in the seventh inning.

All three went down swinging.

“Yeah, definitely felt pretty good out there,’’ Loaisiga said through an interpreter.

When last seen in a Yankees uniform, Loaisiga was opening eyes as a starter, plucked directly from Class AA Trenton.

In his four starts from June 15 through July 2, the Yankees’ first Nicaraguan-born player in franchise history went 2-0 with a 3.00 ERA and struck out 21 batters in 18 innings.

In early July, Loaisiga was sidelined with shoulder inflammation. But as he recovered, the Yankees re-envisioned a role where the rookie right-hander could boost the bullpen down the stretch.

And with an exciting re-debut on Monday afternoon, Loaisiga already has Boone thinking about a potentially larger role.

“As this month unfolds, there’s opportunity to earn a more significant role, and maybe not just length,’’ Boone said of Loaisiga’s new chance to make an impact.

Mostly due to the currently jammed 40-man roster, Yankees general manager Brian Cashman said that lefty Justus Sheffield might not get the chance to pitch in the majors this month.

The organization’s top starting pitching prospect, Sheffield has been pitching in relief lately — a move that had been designed to increase the club’s bullpen depth down the stretch.

The Yankees don’t know when they’re getting closer Aroldis Chapman back from the 10-day disabled list, due to left knee tendinitis — a condition the lefty flamethrower had managed for months before taking himself out of an Aug. 21 game at Miami.

That has rearranged the bullpen order, at a time when lefty Zach Britton is still searching for consistency with his power sinker and with some curiosity about Dellin Betances avoiding another September fade.

On Monday, Loaisiga praised Betances for some key tips in helping him — as Betances did — transition from a starter to a reliever.

“I spoke to Betances, kind of picked his brain about how to prepare for the role and what to expect,’’ Loaisiga said. And thankfully, “everything worked out very well for me today.''

At age 23, Loaisiga made just 25 professional appearances when the Yankees added him to their 40-man roster last November.

Despite his thin pro experience – he’d yet to advance past Class A - and an injury history that cost him two full seasons, the organization feared that he’d be claimed in the Rule 5 Draft if left unprotected.

Loaisiga entered the Yankees rotation in mid-June, when Masahiro Tanaka went on the 10-day disabled list due to two strained hamstrings suffered on the bases against the Mets.

“There’s just an easy way about him, I think he’s really talented,’’ Boone said of Loaisiga at the time. “I think he’s going to be a really good pitcher in this league.’’

And the way Loaisiga carried himself made as much an impression as his electric arsenal.

“Swagger’s not the right word, but there’s just a presence about him,’’ Boone said. “(There’s) a confidence that he’s unaffected by anything going on around him.’’

That disposition could certainly translate into being a reliever, being ready at a moment’s notice – regardless of the inning or situation.

“(I'm) just happy to pitch here and contribute again,'' Loaisiga said.

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