The best trades are the ones where both teams win, when both teams fill holes that need filling. The best trades are the ones where both sides can look back, five years later, and be glad they made the deal.

Only time will tell if the swap agreed to by the Arizona Diamondbacks and Seattle Mariners will turn out that way, but in analyzing the deal, that was certainly the intention in this one.

Last week, the Mariners acquired infielder Jean Segura from the D-Backs in exchange for young hurler Taijuan Walker in a five-player deal that also sent outfielder Mitch Haniger and pitcher Zac Curtis to Seattle and shortstop Ketel Marte to Arizona.

Why Seattle Wanted Segura

After two subpar seasons in which Segura put up 0.0 and 0.3 fWAR as the Milwaukee Brewers' starting shortstop, Arizona acquired him last offseason and moved him to second base, where he had the best year of his career, and one of the best years among all second basemen in 2016.

In 153 games (694 plate appearances), he batted .319/.368/.499 with 20 homers, 102 runs scored, and 33 stolen bases. He had a wRC+ of 126 and an fWAR of 5.0, which ranked seventh-best among MLB second basemen last year.

Only Dustin Pedroia, Daniel Murphy, Ian Kinsler, Brian Dozier, Robinson Cano, and Jose Altuve had better fWARs than Segura did.

With Segura, the Mariners now have one of the top five infields in all of baseball. Here are their stats from last season.

At third base, Kyle Seager ranked sixth in fWAR, and at second, Cano was second overall. The first base platoon of Danny Valencia (who was acquired from the Oakland Athletics last week) and prospect Dan Vogelbach is expected to generate at least a couple wins above replacement as well.

Offensively, there are few infielders who can boast this type of production.

But Seattle also got a pretty decent player in Haniger, who produced well against upper level minor league pitchers last season. In AA, he hit .294/.407/.462 with a wRC+ of 156 in 236 plate appearances, and in AAA, he batted .341/.428/.670 in 312 plate appearances with a 185 wRC+.

He played 34 games for Arizona last year and hit .229/.309/.404 but showed good defense in his brief cup of coffee with the Diamondbacks.

Why Arizona Wanted Walker

Just a couple years ago, Walker was a virtually untouchable prospect for the Mariners, but things are a little bit different now.

Walker has two full seasons of starting under his belt, and he's only been a little bit above league average -- not the ace he was projected to be. Here are his numbers the last two years.

While the results haven't been there, Walker has terrific stuff and, most importantly, is a strike thrower. He's also still just 24 years old this year with a ton of upside.

The Diamondbacks' rotation struggled badly last season, with Zack Greinke (4.37 ERA) and Shelby Miller (6.15 ERA) not living up to their expectations as the team's 1 and 2 starters. However, Robbie Ray emerged as one of the game's best young strikeout pitchers and, with the addition of Walker, gives Arizona a potentially devastating right-handed arm in the rotation.

The D-Backs also got Marte, who quite simply was not very good in Seattle last year.

In 466 plate appearances he batted .259/.287/.323 with just one homer, a wRC+ of 66, and an fWAR of -0.7. Arizona is hoping he'll be more like the player who batted .283/.351/.402 in 247 plate appearances in 2015. But it's the baggage they had to take on in order to land a pitcher with Walker's upside.

Takeaways

The way this trade works out for both teams is if Segura proves 2016 was no fluke and if Walker turns into what most expected of him while he was rocketing up the Seattle minor league system.

Arizona rolled the dice in the hopes of landing a dynamic, young right-handed starter with gobs of upside, while Seattle is hoping Segura will complete an infield that should be one of the best in baseball.