NEW YORK -- Relatively speaking, the Mets have been prudent this season with Edwin Díaz. Only on rare occasions has Buck Showalter asked his closer for more than three outs. Until last Monday, Showalter had never asked Díaz to pitch on three consecutive days.

That evening, a set of circumstances -- Díaz’s low recent pitch counts; a taxed bullpen around him -- prompted Showalter to extend his closer to a third straight night of work. Jogging to the mound in hostile territory in Atlanta, Díaz did what he has all season, throwing 11 pitches and striking out three of the Braves’ best hitters in succession. The next day, he told Showalter he was willing to pitch again.

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This is who Díaz is now. Three-and-a-half years after his oft-criticized trade from the Mariners, and three seasons removed from a nightmarish campaign that soured many Mets fans on the very idea of him as their closer, Díaz is an All-Star -- one of three on a National League roster that also includes Pete Alonso, Jeff McNeil and Starling Marte.

• Alonzo, McNeil, Marte, Díaz are All-Stars

More than that, Díaz might be the most dominant pitcher in baseball.

“He really believes that he’s probably the nastiest closer out there right now,” catcher Tomás Nido said.

The statistics make an easy case for that to be true. For most of the season, Díaz has not only led the Majors in strikeout rate but done so by a wide margin. Entering the final series of the first half, Díaz had fanned 73 of the 142 batters (51%) he had faced. Among pitchers who have thrown even 10 innings, Díaz’s rate of 18.1 strikeouts per nine was 15% higher than that of the Brewers' Josh Hader, who stood in second place, and 213% higher than league average. That sort of gap doesn’t typically occur.

Ask those around Díaz how he’s managed to achieve it, and the initial answer is uniformly one word: confidence. Díaz has always possessed some of the least hittable stuff in baseball, with a fastball that tops out at 103 mph and a slider that, this year, features the highest whiff rate in baseball. But those tools haven’t always translated into success -- certainly not in 2019, when Díaz blew seven saves, lost seven games and produced a 5.59 ERA in his maiden season with the Mets. Regularly, Díaz found himself the recipient of boos at Citi Field. It weighed on him.

“He obviously went through a rough patch,” said Nido, who has known Díaz since they were around 10 years old, “and you can tell that it’s definitely made him a better pitcher.”

The Mets tried everything to fix Díaz. That first offseason, they flew new pitching coach Jeremy Hefner to Puerto Rico to work with the closer. At one point, Mets officials asked Díaz to try to throw his slider over the middle of the plate so that it would actually end up elsewhere; so unhinged was his command.

This year, Díaz has emphasized his slider, throwing it far more often than before. He has become more adept at understanding opposing hitters’ mindsets, which has allowed him to utilize scouting reports effectively. He obsesses over video. And while some mechanical tweaks have stuck, the more significant difference has been Díaz’s ability to repeat his delivery. It’s a similar story to what allowed Jacob deGrom to transform from an excellent pitcher to an all-time great.

“It’s almost like a wild horse that you try to contain,” Hefner said. “You try to cage something that’s beautiful instead of just letting it be.”

In nature, Díaz doesn’t strike the pose of a prototypical closer. He is uniformly friendly and eager to please. His popular warm-up music, “Narco” by Blasterjaxx, eschews hard-edged guitar chords in favor of trumpets and a dance beat. But make no mistake: Much like deGrom, Díaz wants not only to beat his opponents but to embarrass them. As success has piled up for Díaz -- a 1.73 ERA in 37 appearances entering that final series, with 19 saves in 22 opportunities -- his confidence has grown. In text messages with his brother, Alexis, Díaz often boasts about his “nastiness.”

“But it’s not just how confident he is,” said teammate Francisco Lindor. “He’s actually gotten better. So that helps him a ton.”

Lindor recalled one of his first at-bats as an opponent against Díaz, back in 2016, on a night when he knew he would have little chance to catch up to Díaz’s triple-digit fastball. For some reason, Díaz tried to tempt Lindor with sliders instead. The movement on that pitch allowed Lindor to extend his hands and hit a double, which led to the go-ahead run in a Cleveland victory over the Mariners.

Rarely these days does Díaz permit such atrocities, which is why, by early July, he was already a lock to make the National League All-Star team.

This is not Díaz’s first All-Star nod -- he was chosen for the American League roster back in 2018 with the Mariners -- but it is easily the harder-earned of the two. In three years, Díaz went from being one of the game’s most volatile closers to statistically its most unhittable.

He doesn’t plan on reverting back anytime soon.

“My confidence every year is there, but this year, pitching a lot has built my confidence more and more and more,” Díaz said. “If I have the ball in my hand, I can control the game. I can get three outs.”