Diamondbacks move on from pitching coach Brian Kaplan after two-year stint

The Arizona Diamondbacks are turning the page on pitching coach Brian Kaplan, opting not to bring him back after his two-year contract ran out, according to Steve Gilbert of MLB.com. The club will now begin searching for a new voice to lead its pitching staff heading into next season.

Kaplan’s first run as lead pitching coach comes to a close

Kaplan, 44, just completed his first opportunity as a primary pitching coach at the major league level. Before joining Arizona, he spent three seasons on the Philadelphia Phillies’ staff as an assistant pitching coach. The Diamondbacks hired him during the 2024–25 offseason to replace veteran pitching coach Brent Strom.

Teamwide results on the mound did not improve enough to secure Kaplan a new deal. Since the start of the 2025 season, Arizona’s pitching staff owns a 4.34 earned run average, which ranks 22nd in Major League Baseball. Over that same span, the Diamondbacks are ahead of only the Colorado Rockies in strikeout percentage at 19.8 percent, with both seasons under Kaplan producing similar numbers.

This year, the rotation struggled in particular to generate whiffs. Arizona starters ranked 29th in strikeout rate and 28th in swinging-strike percentage, underscoring the club’s difficulty in missing bats. Those issues came alongside injuries and downturns for several key arms.

Injuries, underperformance and a few bright spots

Frontline starter Corbin Burnes has been sidelined for much of the past two years. Late-inning relievers A.J. Puk and Justin Martinez missed significant time in 2025–26 while recovering from elbow surgeries. Veterans Merrill Kelly and Zac Gallen are also coming off what have been described as the worst seasons of their careers.

There were, however, some notable success stories under Kaplan’s watch. Eduardo Rodriguez and Brandon Pfaadt turned in solid campaigns despite only average strikeout totals. Free-agent addition Michael Soroka delivered on a $7.5MM contract, helped in part by the introduction of a cutter that he and the organization incorporated into his repertoire this season.

Arizona also uncovered several bullpen contributors in 2026. Juan Morillo and Brandyn Garcia emerged in leverage roles, while Jonathan Loáisiga re-established himself as an effective ground-ball reliever. Those developments give the next pitching coach a few established building blocks despite the uneven overall metrics.

Lovullo extended as Arizona weighs further staff changes

At the end of the regular season, the Diamondbacks signed manager Torey Lovullo to a new two-year contract, keeping the 11th-year skipper in place. When that agreement was announced, Lovullo declined to say whether he anticipated changes to his coaching staff. Gilbert now notes that additional staff adjustments remain to be determined, with the decision to move on from Brian Kaplan likely only the first step in shaping Arizona’s 2027 coaching group.