Chris Davis was in a horrific slump.

It was September 2015, back when Davis was still one of the most feared hitters in baseball. He'd gone 2-for-his-last-43 and had struck out in more than half of those at-bats. The Baltimore Orioles were getting throttled by the Tampa Bay Rays at home. With Tampa Bay leading 11-0 late, Baltimore manager Buck Showalter used the opportunity to give his workhorses a breather. He pulled Adam Jones. He pulled Manny Machado. He pulled Matt Wieters. As for Davis, who was due up in the bottom of the ninth, Showalter left him in there. He left him in there because Davis begged him to, knowing full well all it takes is one good swing to turn things around. And with Kirby Yates on the mound, the odds of a good swing were better than usual.

Going into that laugher at Camden Yards, Yates was sporting a 9.82 ERA, and had allowed six home runs in 11 innings during a season in which he'd been sent down to the minors on three different occasions. The righty reliever had served up gopher balls in each of his three previous big league appearances, including a two-homer outing against the Texas Rangers that resulted in him getting demoted. Again. A couple weeks later, thanks to September call-ups, he was back in The Show and doing the mop-up thing against Baltimore.

Predictably, Yates started Davis off with a fastball. Just like he'd started off the previous five hitters he'd faced that night with a fastball. At 91 mph, the offering was about letter-high and on the outer edge of the plate, where Davis could easily get his hulking arms fully extended. The ball practically had "Hit Me" inscribed on it. And hit it is exactly what Davis did. He hit it high, he hit it far, and he hit it over the fence. An epic bat-flip ensued.

That one good swing was the start of many good swings for Davis. The next day, he hit two bombs. The day after that, he hit two more. In his final 30 games after taking Yates deep, he hit over .300 and mashed 11 home runs. He finished with an MLB-best 47 dingers, and promptly cashed in by signing a seven-year, $161 million contract that offseason.

For Davis, and pretty much every hitter who faced the reliever, Kirby Yates was just what the doctor ordered.

Padres reliever Kirby Yates went from a mop-up man in the AL East to a lockdown closer on the West Coast. Now he's one of the most coveted names on the trade market -- if San Diego is willing to part with him. Sean M. Haffey/Getty Images

"THAT'S THE WORST I'd ever pitched in my life," says Yates of his nightmare 2015 campaign. "I never struggled that bad. I knew when I'd go to the mound that every hitter who stepped in the box was probably better than what I could do."

Nearly four years later, Yates is back at Camden Yards, a changed man. Now the closer for the San Diego Padres, he has gone from mop-up to lockdown. Standing in front of his visitors locker before a late-June game against the Orioles, he wears a red T-shirt that says "YATERS GONNA YATE" on the front of it. A gift from ESPN NFL Insider Field Yates (no relation), it's but one symbol of the growing attention the 32-year-old hurler is drawing these days.

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Earlier this season, he won National League Reliever of the Month for April, a month-ish (counting the end of March) in which he went 14-for-14 in save opportunities and posted a 0.56 ERA. Three weeks ago, he was named an All-Star for the first time in his career. Now, with the July 31 trade deadline looming and the rumor mill working overtime, it's as if Yates is almost single-handedly powering it.

In a game in which pitching wins championships and bullpenning is all the rage -- especially in the postseason -- you can never have enough arms. And so every year around this time, relievers become the talk of the town. In 2016, Aroldis Chapman and Andrew Miller dominated the deadline buzz. The following season, it was David Robertson and Justin Wilson. Last year, it was Brad Hand and Zack Britton. This time around, it's Yates and ... well ... a few other guys who could best be described as consolation prizes in the Kirby Yates Sweepstakes.

To be clear, the odds of San Diego holding on to Yates are just as good, if not better, than the odds of them trading him. For starters, the Padres, buoyed by the addition of superstar Manny Machado and rookie phenom Fernando Tatis Jr., were in the thick of a crowded NL wild-card race coming out of the All-Star break. As such, they could very well decide to roll the dice and try to sneak into the playoffs this year.

Even if they concede this season and make a couple of trades that could help them in the future, there's an argument to be made that said future could arrive as early as next season. In which case, it wouldn't hurt to have the infinitely affordable Yates -- whose 2019 salary is just $3 million and whose contract runs through 2020 -- lurking in the back end of the Pads' pen. Then there's this: Because Yates is (A) really good, (B) really cheap and (C) would be more than just a two-month rental for the acquiring team, general manager A.J. Preller's asking price might be steeper than contenders are willing to pay.

Regardless of which tack Preller ultimately takes, Yates will continue to be the flavor of the month until the calendar flips to August. It's a testament to the path his career has taken. A testament to the power of change.

THE TRANSFORMATION FROM garbage time to prime time started with a change in repertoire.

Unceremoniously traded twice in a span of six weeks following his miserable 2015 campaign -- both times for a wad of cash -- Yates landed on his feet in the Bronx, where he managed to crack the New York Yankees' Opening Day roster. Prior to that, he'd relied mainly on a four-seam fastball and a slider. But in New York, he found himself surrounded by a bunch of hurlers who were fond of using the split-fingered fastball as a change-of-pace option. Guys such as Nathan Eovaldi, Tyler Clippard and Chasen Shreve. But the splitter that really caught his eye was Masahiro Tanaka's.

"I loved his grip," Yates says. It didn't hurt that Tanaka's split has been one of the most effective pitches in the game. So modeling his hold after Tanaka's -- pointer finger on the left seam, middle finger just outside the right seam -- Yates started messing around with a splitter of his own, but only while playing catch with teammates.

Back home in Arizona that winter, following a mediocre 2016 campaign with the Yankees that featured an ERA north of five and a prolonged stint in the minors, he continued to experiment with the splitter. Five days a week, he played catch with Alex Cobb, a former Rays teammate whose splitter was so filthy earlier in his career it had its own nickname ("The Thing").

"He was able to help with the thought process and how to get consistent break," Yates says of Cobb. "The more I did that, the more comfortable I got, and I was able to take it into the season and explore a little bit. I started seeing results with it, and it just kept getting better."

Eventually, Yates' splitter got good enough that the Padres -- who claimed Yates off waivers in April 2017 -- outlawed his slider. Says longtime San Diego pitching coach Darren Balsley: "We just came to the conclusion as an organization that his split-finger was going to be more successful than his slider."

At first, Yates resisted. After all, he was already 30 years old and had been in the bigs for three years. No way he was going to let a bunch of has-beens and number crunchers he barely knew tell him how to do his job. But in a series of group meetings, Padres brass hammered him with evidence. They showed him video. They presented him with data. Even his teammates got in on the intervention. "If it's difficult for me to catch," veteran reliever Craig Stammen told his throwing partner, "it's going to be difficult for the hitters to hit."

And it has been. Damn near impossible, in fact. Since the beginning of the 2017 season, when Yates first introduced his split-fingered fastball, opponents are hitting .139 against it. No other pitcher in baseball has allowed a lower average against their splitter (minimum 500 pitches). In the past three years since debuting the new offering, Yates has a combined ERA of 2.49, less than half of what it was during his first three seasons in the majors (5.25). Says Balsley: "His slider was a workable major league pitch, but his split-finger is a plus-plus offspeed pitch."

If you ask Yates, though, he'll tell you his splitter isn't the only change he made. That even though everyone makes a big deal out of the pitch and attributes his ascendance to it, there's more to it than that. Way more.

Yates was inspired by Masahiro Tanaka's splitter during their stint together in the Bronx. But honing that pitch wasn't the only turning point for the now-Padres closer. Rick Osentoski-USA TODAY Sports

ARIZONA'S NICE AND all, but it's no Kauai.

Of the 40 Hawaiians who've ever played in the majors, 37 of them came from either Oahu or the Big Island. Pitcher Steve Cooke, a 35th-round pick of the Pittsburgh Pirates who started 88 games during the '90s, was born on Kauai, but he moved to Oregon as a child. The Yates brothers are the other two.

"Kauai's a little harder to leave," says Tyler Yates, a former MLB pitcher and the oldest of the three Yates brothers. "Once you leave, you want to get back home as soon as possible. It's all about the families." In the Yates family, ocean tides are just as much a part of the DNA as nucleotides. Dad Gary, a SoCal native, visited Kauai on a surf trip in 1970 and never left. His three boys (Tyler, Spencer, Kirby) grew up riding the waves that crashed onto the western shores of the island, in the shadows of the Pacific Missile Range Facility. Even as their respective baseball careers took off, the Yates boys always made time for surfing. Maybe a little too much time.

"I just wasn't as disciplined as I needed to be," says Kirby, who signed with the Rays in 2009 after going undrafted out of Yavapai College in Arizona. Every winter, he returned home to the Garden Island, where his catch partner was someone who shared his last name, and his training facility was whichever local field happened to be empty that day. He'd get in the weight room every now and then, but not nearly as much as he'd get in the water. "If the waves were good, I was gonna go surf."

He'd wake up before sunrise, throw his Scovel board in the back of Tyler's black Dodge pickup, and together the two brothers would ride out to Polihale. Or Housings. Or Majors Bay or Kini Kini. Wherever the conditions were best. Spencer, the most avid surfer among them, would usually join them. Even Gary would tag along. Sometimes he'd get out there and body surf. Other times he'd be content to just hang on the beach and watch his boys. On a good day, they'd spend four or five hours, riding waves that were double or even triple overhead. Afterward, on the way back home, they'd stop at the Salt Pond Country Store on Kaumualii Highway and chow down on Spam musubi. As winter breaks go, you could do a whole lot worse.

"It was awesome," says Tyler, who retired from baseball in 2009 and is now a Kauai County police officer. "But [Kirby] realized where his career was going and he knew he was a lot better than that. We all did. Especially by the numbers he put up the minors leagues. So he rededicated himself. He didn't want to suck."

Following the 2016 campaign, instead of going back home like he'd done every year since turning pro, Yates -- who'd posted a 5.23 ERA with the Yankees that season -- decided to hone his craft in Arizona. He worked out there. He played catch there. Instead of pacing off 60 feet at Kalawai Park and pitching to his pops, he threw at a high-tech facility called Pro Advantage. Eventually, he bought a home in Chandler: Like his father before him, what started off as a temporary visit to an unfamiliar land turned into a permanent stay because, well, it just felt like the right place at the right time.

"But [Kirby] realized where his career was going, and he knew he was a lot better than that. We all did. Especially by the numbers he put up in the minor leagues. So he rededicated himself. He didn't want to suck."

At first, the pitcher didn't tell his family. In fact, it wasn't until that first winter, when Tyler Yates called his little bro to find out when he was coming home, that he found out about Kirby's relocation plans.

"Hey, dude," said Tyler through the phone. "You coming home?"

"Nope," said Kirby.

Tyler didn't have to ask why. He'd lived the big league life. He knew exactly what Kirby needed to do.

"Go get it, dude," he told his baby brother. "The beach and surfing will always be here. You only have a short window to play ball, so go ahead and do it."

Kirby did just that.

"I had to get more serious and focused, and understand that if I'm gonna be a big leaguer, this is something I gotta do," says the 5-foot-10 righty, whose left shoulder features a tattoo of the Hawaiian islands, along with the word "Kali," which is his dad's name in Hawaiian (and the middle name of all three Yates brothers). "I was doing it on my own [in Kauai]. There are days you show up in the weight room and you're not feeling it, and you cut your workout short because you got no motivation or nobody there to push you."

In Arizona, Yates had a small army of fellow pitchers to push him, many of whom were former teammates from his days with the Rays. Guys such as Drew Smyly, Matt Moore and Merrill Kelly. He had Cobb, who became his splitter whisperer. He had a real training facility and, for the first time in his career, a real personal trainer. His hips became more flexible. His core grew stronger. Although the professional development wasn't without personal cost, Yates wouldn't do anything differently.

"It was hard to do," he says of making the decision to give up his winters in Kauai. "But it's changed my career."

IT'S NOT LIKE Kirby Yates doesn't ever get the chance to see his family anymore.

Earlier this month, they flew to Cleveland for the All-Star festivities. Before that, in June, they visited during a homestand in San Diego. Even though Petco Park is nearly 3,000 miles from the Aloha State, it's practically around the corner compared to, say, Tampa or the Bronx. Of course, the way Yates has been dominating -- his 1.05 ERA through July 22 was best among MLB relievers -- he could find himself on the move again in the very near future.

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With one week left until the trade deadline and a league littered with patchwork bullpens, the kid from Kauai is at the tippy top of many a general manager's wish list. That is, if the Padres decide to part with him.

"He's as good a reliever as there is in the game today," says one NL evaluator. "But relievers are fickle. If it were me, I would trade him. I think they trade him."

Regardless of what goes down between now and the end of the month, be it rumors or the real deal, Yates doesn't sound like someone who's about to let himself get distracted.

"This is the position I always strived to be in," he says. "It's not like I was pitching terribly and saying, 'Yeah, I want to be a middle reliever for the rest of my life.' Everybody in the bullpen wants to be a closer. Maybe everybody else didn't think I was capable of doing it, but I did. I don't want to take my foot off the pedal."

Not that his teammates are the least bit worried about that.

"He's been at a place in his career where he was struggling," Stammen says. "He understands that things can change on a dime. Right now he's having a ton of success and things are going well. He's going to ride that wave as long as he can."

It might not have the size or the shape of the waves back on Kauai, but for now, it'll have to do.