MLB Mock Trade: Arizona Diamondbacks Deal Josh Naylor To Seattle Mariners For Ryan Sloan

The Seattle Mariners are in need of a power boost at first base, and Josh Naylor of the Arizona Diamondbacks could be an ideal trade deadline acquisition.

Arizona Diamondbacks first baseman Josh Naylor (22) strikes out during the second inning against the Los Angeles Angels at Angel Stadium. | Jayne Kamin-Oncea-Imagn Images

With Cal Raleigh delivering an epic catcher season (.255/67/38/83/11 over 364 at-bats), the Seattle Mariners’ offense would be in the dumpster in 2025. Their stud, franchise bat (Julio Rodriguez) continues to underachieve expectations (.249 over 409 at-bats with 65 runs, 14 home runs, 51 RBIs, and 19 stolen bases). Four players have accounted for 61.6% of their 138 home runs (6th). 

Seattle sits eighth in runs (467), seventh in RBIs (449), and fifth in steals (90) after 100 games. Their offense lacks a viable power anchor at first base. Ben Williamson continues to bring quiet production to third base (.259/35/1/19/3 over 251 at-bats). The Mariners expect Cole Young to be a helpful bat in the future, but he has yet to find his rhythm at the plate (.254/14/2/12 over 126 at-bats). 

Injuries to three frontline starters have led to Seattle ranking lower than expected in ERA (3.92). George Kirby’s ERA (4.65) is out of line when looking at his WHIP (1.13). Bryce Miller is trying to rebound from an early-season elbow issue, but his struggles (5.73 ERA and 1.54 WHIP) suggest an injury that may require surgery down the road.

Seattle Mariners starter George Kirby (68) delivers a pitch during the second inning against the Pittsburgh Pirates at T-Mobile Park. | Stephen Brashear-Imagn Images

The Mariners have worked through some early-season bullpen issues, giving them four trusted relievers: Andres Muñoz, Matt Brash, Gabe Speier, and Eduard Bazardo. They sit 12th in bullpen ERA (3.88), with 24 wins, 16 losses, and 23 saves. 

Based on their team structure in late July, Seattle needs a bridge power bat at a corner infield position or a long-term solution at first base. Josh Naylor appears to be the top option who will be a free agent in 2026. Wilmer Flores was on a career pace earlier in the year for the Giants, but his bat and playing time have faded over recent weeks. He would also offer some value at third base. Eugenio Suarez is the top free agent option at third base, with Yoan Moncada being the cheap “fill a gap” choice.

Based on expected price point, Josh Naylor would be the more attainable bat for the Mariners. Arizona needs long-term starting pitching help, and Seattle has younger starting pitching depth at the major league level, allowing them to move some of their minor league pitching depth for an offensive player.

Possible Minor League Pitchers:

• Jurrangelo Cijntje (SP) – The Mariners drafted him 15th overall after showing growth in 2024 at Mississippi State (8-2 with a 3.87 ERA, 1.103 WHIP, and 113 strikeouts over 90.2 innings). In his first season in the minors at High A, home runs (11) and walks (34) have been a problem over 62.0 innings, leading to a 4.65 ERA and 70 strikeouts. His fastball has triple-digit upside, and Cijntje brings a rare skill set when he can pitch right and left-handed.
• Ryan Sloan (SP) – He brings a workhorse profile (6’5” and 250 lbs.) while featuring a mid-90s fastball, along with a high-ceiling changeup and a winning slider with side action. Over 15 starts at A-ball, he posted a 3.43 ERA, 1.15 WHIP, and 64 strikeouts over 57.2 innings. Sloan completed the fifth inning in only one game. 
• Brandyn Garcia (RP) – Over three seasons in the minors, Garcia posted a 2.44 ERA, 1.23 WHIP, and 188 strikeouts over 162.1 innings. Seattle shifted him to the bullpen this year at AA, and the Mariners called him up on Monday. In his major league debut, he allowed a run and five baserunners over one inning. His sinker sits in the upper 90s.

Seattle Mariners - Arizona Diamondbacks MLB Mock Trade

The Diamondbacks’ starting point to move Josh Naylor to Seattle should be Ryan Sloan. He fits their long-term pitching need, but the Mariners must decide if a rented bat is worth the ceiling of their young pitching prospect. Ultimately, the viability of this trade depends on other interests in Naylor’s bat.