The Arizona Diamondbacks’ bullpen has been under fire all season, and this week, the team finally made its first meaningful round of changes in an attempt to stop the bleeding.
Arizona officially cut ties with struggling left-hander José Castillo, trading him to the New York Mets in exchange for cash considerations. While not a blockbuster by any stretch, the move provides at least some value for the D-backs, who had already designated Castillo for assignment earlier in the week. By shipping him to New York, the organization avoided losing him for nothing while clearing a much-needed roster spot.
Diamondbacks shake up bullpen as struggles mount: Castillo traded, Mantiply demoted, Graveman debuts
Veteran right-hander Kendall Graveman was activated and made his long-anticipated season debut on Wednesday night. The 34-year-old, who signed with Arizona in the offseason but had yet to pitch in 2025 due to injury, provided stability the team was looking for in his first appearance on the mound. Graveman worked a scoreless inning allowing one walk but otherwise keeping things clean.
For a Diamondbacks bullpen that ranks near the bottom of Major League Baseball in many meaningful categories — ERA, WHIP, opponent batting average — any sign of life is welcome. Graveman’s debut, though far from spectacular, marked a step in the right direction for a relief unit that has let too many winnable games slip away.
One of the biggest contributors to those struggles, left-hander Joe Mantiply, was also sent packing — but only on a shuttle to Triple-A Reno. The former All-Star has been in a free fall all season, surrendering 14 earned runs in just 6.1 innings since his last scoreless outing on April 5. His season stats are pretty disastrous sporting a 15.83 ERA and a 3.00 WHIP. Although Mantiply has only walked three batters, opponents have battered him for 26 hits in just 55 plate appearances. The demotion was long overdue, and the D-backs will now look to others to stabilize their left-handed relief options.
Help may be on the way soon. Hard-throwing right-hander Justin Martinez, who landed on the injured list earlier this month with shoulder inflammation, is nearing a return. His return would add much-needed velocity and swing-and-miss potential to Arizona’s bullpen. However, the D-backs are still awaiting updates on left-hander A.J. Puk, who remains sidelined with elbow inflammation.
While these transactions don’t solve all of Arizona’s bullpen woes, they represent the start of a long-overdue shake-up. With Graveman back, Martinez on the mend, and the front office showing a willingness to make tough calls, the Diamondbacks are signaling that they’re not content to watch the season slip away.