MILWAUKEE -- It was in Biloxi, Miss., sometime in late 2015. Josh Hader had a busy summer between pitching for Team USA in the Pan American Games and being traded for the second time in his young professional career, this time from the Astros' organization to the Brewers as part of the blockbuster that sent Carlos Gómez and Mike Fiers to Houston. Looking back now, no move short of the Christian Yelich trade had a bigger impact on the Brewers’ quick transition from rebuilding to contending in about three years.

At the time, Hader was still a starting pitcher getting grounded in another new system. The Brewers sent their roving pitching coordinator, Chris Hook, to have a look.

“I remember talking to him in the weight room,” Hook said. “Like, 'Hey man, what have you been doing?' He was like, 'Oh, I was just in the Olympics and I was out there really letting it go as a reliever. Man, that's really, really comfortable for me.' I just remember him back then speaking about throwing in the Olympics and letting it go and, 'Man, that was fun. I really enjoyed that.'”

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Today, that’s what Hader gets to do. After transitioning him to the bullpen and using him in multiple-inning stints, always with extensive rest between outings, the Brewers slowly watched Hader evolve into what he is now: Essentially, a traditional, one-inning closer.

Hader, who occasionally sparred with the club in arbitration as the sides struggled to assign value to his unique usage, has embraced the evolution. And he’s made it work in two important ways. One, he has added strength and durability to his naturally wiry frame over the years to bounce back better from outing to outing, which is imperative for a pitcher in a closer’s role. Two, he has become more efficient with increased usage of two offspeed pitches -- a slider that was long part of his repertoire but became a significantly bigger part of his arsenal during the shortened 2020 season, and a changeup with which Hader had tinkered for years and years, but finally was honed in 2021.

So, a pitcher that was the National League Reliever of the Year in 2018 and ’19, and a NL All-Star both seasons, has become a totally different pitcher. His fastball usage went from 82.9 percent in ‘19, according to Statcast, to 67.7 percent in ’20 and 65.2 percent entering the Brewers’ final series of the first half in ’21. His slider usage, meanwhile, went from 15.5 percent in ’19 to 32.3 percent in ’20 back down to 27.8 percent in ’21 because of the introduction of that changeup, which he is throwing seven percent of the time.

And the results continue to be excellent. Hader became the third pitcher in Brewers history to begin a season 20-for-20 in save opportunities before experiencing his first blown save in Game 1 of a doubleheader against the Mets on Wednesday. José Peraza’s tying home run was the first homer off Hader all year.

“Completely different,” Hader said of his approach to pitching in 2021. “There's a process to everything we do, the way we learn about this game and the way we have to adjust because there's so much information out on us now that they know what to expect. At the end of the day, you have to try and use everything you can to your advantage because these guys are good enough to sit on that one pitch -- the fastball was my one pitch, but now I'm able to use different pitches to be able to make that fastball look a little bit better. I think that's the cool thing. That's how you stay here as long as you can, is adapting to the league itself.”

Part of this is a matter of technology. High-speed cameras and radar today allow pitchers to get instant feedback on every pitch, even when they are at home throwing in the backyard during the offseason. The tech has evolved right alongside Hader, such that a process of developing a pitch by feel or feedback from hitters’ swings can now be done by viewing spin rate and spin access and velocity, right on the spot.

“Even back then, the changeup was something that he was working on,” said Hook, referring to their first meeting in Biloxi. “But now with the Edgertronic, with the TrackMan, we can really see if it's good or not. And that's what really took him forward.”

The key, Hook said, is that Hader bought in.

Hook thinks of Hader’s evolution like this: “It’s just being stubborn to be great.”

That stubbornness is the common thread between the Brewers’ quartet of All-Star pitchers, Hader and starters Brandon Woodruff, Corbin Burnes and Freddy Peralta. Hader and Woodruff found success early. Peralta and Burnes took more of a winding path to the Midsummer Classic, especially Burnes, who achieved as a reliever in 2018, struggled as a starter in '19, then had to remake his arsenal and his mental approach to rediscover success in '20 and ’21. Ditto for Milwaukee's fifth All-Star representative, catcher Omar Narváez, who endured his worst offensive season in ’20 and spent the winter making changes to regain his form as a hitter.

But Hader’s desire to evolve came against the backdrop of the greatest immediate success. He didn’t debut in the Major Leagues until midway through the 2017 season, but already he’s tied with Dan Plesac for the most career All-Star appearances -- three -- for a Brewers reliever. The record for All-Star Game berths for a Brewers pitcher is four, by Ben Sheets.

“It's really amazing to think that Josh Hader is getting better,” Brewers manager Craig Counsell said. “We see this improvement every season and I just think that's such a credit to him as a professional, that he achieved great things immediately when he walked into this league, and yet he still found ways to get better. I really admire that. It's a great trait that he has and that's why he's going to be in the league for a really, really long time.”

Said Hook: “It's just like, he never stops. Some people, when they have success here, they don't want to change anything. These guys don't think that way. It is always looking to get better.”