It’s no secret that we here in The Ringer’s baseball department love us some Jerry Dipoto. The 50-year-old former Colorado Rockies closer has been baseball’s fidgeter-in-chief during his three years running the Seattle Mariners, pulling off a frenetic series of trades that made him one of the select few sports figures (along with Carmelo Anthony) that this publication has immortalized in song. But while many of those trades have just been tinkering around the edges, one has the Mariners in position to make the playoffs for the first time in 17 years. That deal: pitcher Taijuan Walker and shortstop Ketel Marte to Arizona for pitcher Zac Curtis, shortstop Jean Segura, and outfielder Mitch Haniger. It’s Dipoto’s magnum opus, and perhaps the single biggest reason we’re on track to see Seattle in the playoffs.

Most high-profile baseball trades involve two or more trade partners with wildly differing goals. One team needs pitchers, the other needs position players, and so two marginal players of similar value are swapped to fill both teams’ needs—like the Matt Harvey–for–Devin Mesoraco trade between the Mets and the Reds. Most frequently, though, one team wants to contend now and wants established big leaguers, while the other wants prospects—Manny Machado for five Dodgers prospects, or Brad Hand and Adam Cimber for Francisco Mejía.

However, Seattle is in a position that’s forced Dipoto to get creative. The 2015 Mariners finished 76-86, and most of their best players—Kyle Seager, Robinson Cano, Nelson Cruz, Hisashi Iwakuma, Félix Hernández—were in their late 20s or early to mid-30s, and therefore not likely to improve. Seattle wanted to contend immediately, but that offseason, Baseball Prospectus ranked the Mariners’ farm system the 28th-best in baseball, which not only meant that internal reinforcements weren’t coming, but that Dipoto didn’t have a wealth of prospects to trade for big league talent.

Even when Dipoto has tried to trade prospects for big league help, he hasn’t always come out ahead—he traded Brazilian left-hander Luiz Gohara to Atlanta for outfielder Mallex Smith and reliever Shae Simmons, then flipped Smith, lefty Ryan Yarbrough, and minor league infielder Carlos Vargas to Tampa Bay for Drew Smyly. Yarbrough’s been a roughly league-average pitcher in 93 2/3 innings for the Rays this year, while Gohara was a top-50 prospect last offseason. (He still has the potential to wash out; left-handers with upper-90s fastballs don’t grow on trees.) Meanwhile, Simmons and Smyly both got hurt and combined to throw 7 2/3 innings in their Mariners careers. But Dipoto’s trade record isn’t all bad: He’s made the most of some middling prospects, acquiring Denard Span, Alex Colomé, Dee Gordon, and Mike Leake in what essentially amount to salary-dump trades.

And Dipoto hasn’t been able to simply spend his way up the standings. Seattle has run competitive, but not earth-shattering payrolls, mostly in the $150 million range, placing the Mariners in the middle third of MLB teams. And finally, first place in the AL West isn’t some vacant throne to be snatched up by whoever sleepwalks into it—this has been a tough division in the 2010s, as first the Rangers and then the Astros built and cashed in on ridiculously talented farm systems. The A’s have been competitive for stretches, and the Angels have attempted to surround Mike Trout, the best player in baseball, with a team worthy of his talents.

For two years, Dipoto was one of the busiest GMs in baseball, but for all his hyperactivity, the Mariners improved, though not by much. In 2016, Dipoto’s first year, the Mariners went 86-76, falling short of the AL wild card in the season’s final week. In 2017, they dropped to 78-84 after a rash of injuries. But this year, the Mariners are 60-40, finally in position to grab that elusive postseason berth. All thanks to challenge trades.

Trades come about because not every player is worth the same to every team. Consider the deal the Padres and Indians pulled off last week. San Diego isn’t going to contend this year, or maybe even next, so having a great bullpen doesn’t make much of a difference for the team, while a minor league catcher who could become a star in two or three years would be incredibly valuable. Cleveland, however, is definitely going to the playoffs and needed relievers badly. While it would have been nice to hang on to Mejía, the Indians don’t need him right now—certainly not with All-Star catcher Yan Gomes in the fold already. Since the Padres’ and Indians’ needs are so different, both teams pretty clearly come out ahead.

That’s the way most trades work nowadays. As front offices have become smarter, their player-evaluation methods have not only gotten better, they’ve also gotten similar, so baseball marches predictably down the road to Pareto optimality.

But every so often, one team will consider a trade of two (or more) players of similar age and talent. It’s GMs or scouting departments saying to one another: “We know something about these two players that you don’t,” which is audacious and, frankly, quite exciting—hence the term “challenge trade.” But it’s rare. For starters, each team typically knows its own players better than any trade partner does, which makes that kind of informational asymmetry tough to come by, so it’s tough to find two trade partners who both think they can get one over on another team. And while winning a challenge trade makes you look like a genius, losing one makes you look like a sucker, and GMs, whose careers live and die in the realm of public opinion, are wise not to undertake that risk rashly.

No franchise knows that better than the Mariners. Probably the most famous challenge trade of the past decade was the work of Dipoto’s predecessor, Jack Zduriencik. On January 23, 2012, he made a trade that essentially amounted to sending pitcher Michael Pineda to the Yankees for catching prospect Jesús Montero. Pineda had made the All-Star team as a 22-year-old rookie and looked like the John Smoltz to Hernández’s Greg Maddux. Montero, a consensus top-10 prospect three years running, looked like the next Miguel Cabrera even if he couldn’t stay behind the plate.

The deal turned out to be a disaster for both sides. Pineda got hurt and missed the next two seasons, while Montero forgot how to hit and struggled with his fitness. Two years after the trade, Mariners scout Butch Baccala had an ice cream sandwich delivered to Montero in the dugout during a minor league game, by way of mocking Montero for being overweight. An unhappy Montero went into the stands and confronted Baccala and was suspended for the rest of the year for his trouble. Zduriencik was fired a year later, one of the last big league GMs to lose his job not just as a loser, but as a laughingstock.

None of that seemed to faze Dipoto. Last summer, he pulled off a challenge trade with the St. Louis Cardinals, parting ways with 22-year-old power-hitting outfield prospect Tyler O’Neill, a fringe top-100 guy. In return, the Mariners received former first-rounder Marco Gonzales. Gonzales struggled to find his footing in St. Louis, but has posted a 118 ERA+ in 20 starts for the Mariners this year, making him an incredibly important contributor on a team that was frequently short on pitching in 2017.

Part of that pitching shortage, however, is the result of trading Walker to Arizona before the 2017 season in the Segura-Haniger deal. The Mariners took Walker 43rd overall in 2010, and he rose through the minors quickly—he debuted in 2013 at just 21 years old, looking every bit like a future ace. But over the course of four seasons in Seattle, Walker was sometimes hurt, sometimes ineffective, sometimes both: He finished his Mariners career with a 93 ERA+ in 357 innings.

Marte made his big league debut in 2015, also at age 21, and hit .283/.351/.402 as a rookie in 247 plate appearances. In 2016, his numbers dropped to .259/.287/.323. Both Marte and Walker were still young enough to hold significant potential, but had failed recently enough in the past that they counted more as post-hype sleepers than certain future building blocks.

For those two players, Dipoto got back Curtis—a lefty reliever who appeared in three games for the Mariners before ending up on waivers—Haniger, and Segura.

The season before the trade, Haniger hit .341/.428/.670 in 74 games at Triple-A, but those numbers aren’t as impressive as they look. For starters, Haniger was 25, positively ancient by prospect standards, and he put up those numbers in the Pacific Coast League, which is an archipelago of high-altitude bandboxes so hitter-friendly that some teams just don’t ever send their top pitching prospects to Triple-A for fear of messing with their mojo. When Haniger finally got to Arizona, he hit a pedestrian .229/.309/.404 in 123 big league plate appearances.

Segura had a more complicated and tragic backstory. A former top-100 prospect, he was traded to Milwaukee as part of the deal that sent Zack Greinke to the Angels in 2012. Segura made the All-Star team in 2013, when he displayed the speed, defense, and contact skills that had made him a vaunted prospect and answered questions about his plate discipline and power.

Then, in 2014, Segura’s 9-month-old son died unexpectedly, and the then-24-year-old went into a tailspin. Segura hit .252/.285/.331 over his last two years with the Brewers and almost quit baseball. It was only after leaving Milwaukee in a five-player trade that Segura returned to form. In 2016, his only season in Arizona, Segura hit .319/.368/.499 with 33 stolen bases and led the National League in hits.

Among the two shortstops in the deal, Segura was the better player, but he was also three and a half years older than Marte, and while Walker had been frustrating in Seattle, he’d also had some track record of big league success. Haniger, by contrast, was an unknown quantity.

After being traded, Walker had the best season of his career, making 28 starts with a 135 ERA+ as part of one of the best rotations in baseball. Marte struggled with injuries and hasn’t hit like he did as a rookie, but he played well in 73 games in 2017. Well enough, in fact, for the Diamondbacks to offer him a five-year contract extension, with team options that could keep him in Arizona through 2024. Last October, both Marte and Walker appeared in the playoffs for the first time in their careers.

Even though Walker will miss the rest of this season after undergoing Tommy John surgery, the Diamondbacks made out pretty well, which illustrates the peril of the challenge trade. Walker and Marte are both young, above-average players under team control for years to come, but they’re not as good as the players Arizona gave up.

Since the start of the 2017 season, 27 players have played at least 150 games in the majors with at least half of their appearances at shortstop. Among those players, Segura is fifth in bWAR (trailing Didi Gregorius by a tenth of a win), sixth in OPS+ (five points behind Corey Seager), fourth in win probability added, and tied for third in stolen bases. This year, he won the final vote for the American League All-Star team and went 2-for-2 with a home run, three RBIs, and two runs scored once he got into the game.

Haniger also made the All-Star team, because despite having almost no track record of big league success before joining the Mariners, he’s been one of their most valuable players since the trade. Haniger hit .282/.352/.491 with a 126 OPS+ in 410 plate appearances last year, and so far this season, he’s been just as good (.271/.361/.483) in almost exactly as many plate appearances. There are 56 players who have played at least 150 games with at least half of their appearances in an outfield corner since the start of the 2017 season. Among those, Haniger is ninth in bWAR, tied for seventh in OPS+, 12th in WPA, and tied for eighth in wins above average.

Seattle’s return from that trade represents the upside of a challenge trade if you win it. The Mariners gave up two above-average, cost-controlled players but got back two All-Stars who are probably both going to get some down-ballot MVP votes. Right now, Haniger (3.6) and Segura (3.1) are the two most valuable Mariners according to bWAR. The only Mariner who’s within even a win of Segura is Gonzales, the other player Dipoto picked up in a challenge trade in the past two years.

By some combination of good scouting and luck, the Haniger-Segura trade has kept the Mariners not only in the playoff race, but in a playoff position. The answer to “What did Jerry Dipoto do?” is always changing, but nothing Jerry Dipoto’s done has been more important than this deal.