• Jeff Passan, ESPNJul 31, 2023, 06:10 PM ET

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      Author of “The Arm: Inside the Billion-Dollar Mystery of the Most Valuable Commodity in Sports”

The struggling Diamondbacks acquired closer Paul Sewald from the Seattle Mariners on Monday, hoping to shore up a bullpen that has faltered over the past month and taken Arizona from leading the National League West to out of a playoff spot.

While the Diamondbacks (56-50) and Mariners (54-51) have near identical records, Seattle took advantage of a thin pitching market and received three hitters in return: rookie outfielder Dominic Canzone, utilityman Josh Rojas and Ryan Bliss, a Double-A middle infielder.

With the Diamondbacks’ window of contention opening, they were searching for more of a long-term solution than a rental player, and they got it in Sewald, who is under team control through the end of the 2024 season. The 33-year-old had been a stalwart in the Mariners’ bullpen since joining the team in 2021, saving 52 games, and will take over the role after Arizona spent the season using a committee.

In 43 innings this season, Sewald has struck out 60, walked 14 and posted a 2.93 ERA while saving 21 games in 24 opportunities.

In the past 30 days, the Diamondbacks’ bullpen posted a 6.37 ERA, better than only Washington’s 7.22.

Arizona stayed busy Monday night, acquiring infielder Jace Peterson from the Oakland Athletics for righty Chad Patrick.

Peterson, 33, saw the majority of his time at third base for Oakland this year, hitting .221 with six home runs and 11 steals. Patrick had been pitching at Double A, going 4-7 with a 4.71 ERA.

The Mariners’ offense struggled this season after they made the postseason for the first time in two decades in 2022. To address it, they moved Sewald — the second time in three years they dealt their closer near the deadline, with Kendall Graveman going to Houston in 2021.

Canzone, who turns 26 next month, spent most of the season destroying Triple-A pitching with a 1.065 OPS in 304 plate appearances. In his first big league stint, he has hit .237/.293/.368, and with Jarred Kelenic on the injured list and Teoscar Hernández a trade candidate, Canzone could see regular time in a corner-outfield spot.

Bliss, 23, was as good at Double-A as Canzone was at Triple-A, hitting .358/.414/.594 with 12 home runs and 47 RBIs. Mostly a second baseman, the 5-foot-6 Bliss, who represented the Diamondbacks in the Futures Game this year, has hit .196/.274/.357 after a promotion to Triple-A.

Rojas, 29, joined the Diamondbacks four years ago in a deadline deal for Zack Greinke. After a solid 2022, he has struggled to hit this season with a .228/.292/.296 line and no home runs in 216 plate appearances. He has three years of team control and will be arbitration-eligible for the second time this winter.