Yankees closer Aroldis Chapman throws a bullpen session in Tampa...

Yankees closer Aroldis Chapman throws a bullpen session in Tampa during spring training on Feb. 16, 2019. Credit: Newsday/Thomas A. Ferrara

TAMPA, Fla. — The Yankees’ bullpen was among the most potent in the big leagues in 2018.

The group ranked fourth in the majors in ERA (3.38), but that didn’t even begin to tell the story.

The unit collectively accumulated a league-leading 753 strikeouts in 594 2⁄3 innings, second-most by a bullpen in major-league history (the Rays, who frequently used relievers as “openers” last year, got 754 strikeouts in 824 1⁄3 innings from their bullpen).

In ranking first in baseball with a 9.7 WAR, per FanGraphs, the Yankees’ bullpen featured four of the majors’ top 17 relievers in strikeouts — Dellin Betances (third with 115), Chad Green (tied for 11th with 94), Aroldis Chapman (tied for 14th with 93) and David Robertson (17th with 91).

Super-impressive numbers all — and numbers more than a few think can be surpassed by this year’s unit.

“They really have five guys with closer stuff,’’ one opposing team scout said early in spring training. “You’re doing good if you have one or two.”

Robertson, whom the Yankees did not try to retain, signed a free-agent deal with the Phillies. But Chapman, Betances (he starts the season on the injured list) and Green are back, as is Zack Britton, a trade-deadline acquisition in 2018 who re-signed as a free agent and is the healthiest he’s been since 2016, when he posted a 0.54 ERA with the Orioles.

Replacing Robertson? Righty Adam Ottavino, the New York City native whom the Yankees brought aboard as a free agent on a three-year $27 million deal. He is coming off a season with the Rockies in which he struck out 112 in 77 2⁄3 innings.

Yankees reliever Adam Ottavino pitches a bullpen session during spring...

Yankees reliever Adam Ottavino pitches a bullpen session during spring training in Tampa on Feb. 15, 2019. Credit: Newsday/Thomas A. Ferrara

Jonathan Holder and Tommy Kahnle, both of whom were mostly terrific throughout spring training, are capable of big strikeout numbers and give Aaron Boone even more options.

“I don’t really rate them because it’s going to come down to performance at the end,” said Larry Rothschild, who is entering his ninth season as Yankees pitching coach and has seen his share of standout bullpens in that time. “They have the potential to be really, really good.”

The only definitive role, as of now, belongs to Chapman, who will close. Otherwise, it could be any reliever at any time.

“A lot of depth,” Green said of the arms. “Especially to give guys a day [off] here and there is huge. Obviously, it’s a long season, so if you need to give a Chapman a day, Britton can close, Dellin can close. Pretty much we have at least [five] closers down there, so it’s going to be fun to watch for sure.”

GRADE: A

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