Jose Butto of the Mets throws a pitch against the Marlins...

Jose Butto of the Mets throws a pitch against the Marlins during the first inning at loanDepot park on Sept. 18 in Miami, Fla. Credit: Getty Images/Rich Storry

PHILADELPHIA — When the Mets needed starter after starter after starter this season, Jose Butto almost never was their choice. Some within the organization were skeptical of his ability to survive as a starting pitcher in the majors, and his poor numbers in the minors did little to convince anyone otherwise. So except for an occasional cameo, they left him there, trying other arms instead.

Along the way, though, something funny happened: Butto’s two pitches became four when he improved one and introduced another. Now, amid a five-outing stint in the rotation that has served as an audition for 2024, he has impressed with a 2.08 ERA, a .194 opponents’ batting average and more than a strikeout per inning heading into Sunday’s start against the Phillies.

“He’s answered the bell,” pitching coach Jeremy Hefner said. “It was one of the things we set out to do with him in September, give him this opportunity, a little bit of a runway to showcase his abilities. He’s worked really hard throughout his career. He deserved the opportunity to come up here and do this.”

Manager Buck Showalter said: “You can tell he’s more confident about attacking hitters. There’s been a good presentation in how he’s looked competing.”

A key to small-sample success for Butto, a 25-year-old rookie righthander: an expanded menu of pitch options months in the making. He already had a mid-90s fastball and a changeup that always has been his best offering, but he needed more to stave off the idea that he is destined to be a reliever.

First came a slider, which basically has replaced a curveball as his breaking ball of choice. He tinkered all offseason with different grips and found one that he liked right before spring training. But during his time in major-league camp, he wasn’t quite comfortable with it and it acted more like a cutter — higher velocity, less movement. Fine, but not really what he wanted.

Through experimentation and repetition with Triple-A Syracuse, Butto learned to throw the slider more softly, which led to more movement. After Butto’s recent outings, Showalter has complimented the “shape” of the pitch, which he called “usable.” That sounds like a low bar, but it represents progress.

“That pitch has helped me a lot this year compared to years past,” Butto said through an interpreter.

Hefner said: “The slider has always been something that we — I wouldn’t say a struggle, but it’s always been the thing he needs to work on. He’s gotta get his slider better. Sometimes it’s really big, sometimes it’s really short. We’ve kind of found a happy medium with it.”

Later came a sinker. He always had thrown one in practice, never in the real thing. In early August, he decided sort of on a whim to try it after a conversation with Syracuse pitching coach Kyle Driscoll.

On the day he finally broke it out, Butto tossed his first scoreless outing in four months, 5 2⁄3 innings against the Yankees’ Scranton/Wilkes-Barre affiliate.

“I never felt that comfortable to actually use it in games,” Butto said. “I figured because I rely strongly on the four-seamer, I could implement that into my repertoire and try to get guys out, whether I fall behind in counts and try to get them to roll over and ground into a double play or try to get a fly ball. It was something that could help.”

It very much has.

“The sinker probably helps him more than any other pitch, especially against the righties,” Hefner said. “It gives him that other dimension to navigate a lineup and not rely just on his four-seamer or just on his changeup.”

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