Diamondbacks to part ways with pitching coach Brian Kaplan

Arizona will not bring back pitching coach Brian Kaplan when his two-year contract expires, per MLB.com's Steve Gilbert, as reported by Anthony Franco of MLB Trade Rumors. The Diamondbacks will look elsewhere for their next lead pitching instructor, though Gilbert notes it is to be determined whether any further staff adjustments are coming.

What happened

Kaplan's two-year deal ran its course, and Arizona chose not to extend it. Per the report, this was Kaplan's first stint as a lead pitching instructor at any level; before arriving in the desert, he had spent three years with the Phillies as an assistant pitching coach. The Diamondbacks tabbed him over the 2024-25 offseason to replace Brent Strom.

The timing lands a few days after Torey Lovullo signed a new two-year contract to continue managing the club. At the time Lovullo's extension was announced, the 11th-year skipper declined to say whether he would make changes to his coaching staff. Kaplan's departure answers part of that question, though the rest of the staff picture remains open.

Why it matters

Pitching coach transitions are among the quieter but more consequential offseason moves a club can make, and Arizona's situation gives the next hire a genuinely complicated brief. The staff's two-year body of work, per the report, was middling at best: the Diamondbacks ranked 22nd in ERA at 4.34 and ahead of only the Rockies in strikeout percentage at 19.8% since the start of 2025. Those numbers were roughly consistent across both seasons, which is its own kind of verdict.

The contact-management problem was sharpest among the starters. Per the report, Arizona's rotation ranked 29th in strikeout rate and 28th in whiff percentage in 2026 — numbers that are hard to explain away entirely by personnel, and equally hard to pin entirely on coaching. The honest answer, as the report implicitly acknowledges, is that the two-year ledger is a tangle of injury, underperformance, and genuine development, and whoever takes the job next inherits all of it.

The numbers

The Diamondbacks finished 86-76 (.531), sitting 3rd in the NL West, 14 games back in the division, and eliminated from both the division race and the Wild Card race. They closed the season on a two-game losing streak and ranked 4th in the Wild Card standings, 2.0 relative to the cut line.

Those team-level outcomes frame the pitching staff's two-year arc. A 4.34 ERA ranked 22nd across the league. A 19.8% strikeout percentage that cleared only Colorado. A rotation that ranked 29th in strikeout rate and 28th in whiff percentage in the most recent season. The desk will note, without editorializing, that "22nd" and "29th" are not numbers a front office frames and hangs on the wall.

Where the club stands

At 86-76, Arizona's season is over. The club is eliminated from the division and the Wild Card, and the attention now shifts fully to the offseason. Lovullo is locked in for two more years. The coaching staff around him is, at least in one significant spot, an open question.

Per a separate report from earlier this week, GM Mike Hazen confirmed the club will prioritize adding left-handed bats at first base and designated hitter, targeting upgrades after the team struggled against right-handed pitching in 2026. And per another recent report, Ketel Marte's future with the organization is uncertain following conduct and absence issues in 2025, with executives signaling a trade is possible despite Marte holding full no-trade rights. The pitching staff search, then, is one piece of a broader offseason reconstruction that is already taking shape.

What we don't know yet

The report is clear that further coaching staff changes are to be determined. Kaplan's departure is the only move addressed by the reporting; everything else around the staff remains open. There is no named candidate for the pitching coach role, no timetable for a hire, and no indication of how extensively Lovullo and the front office intend to reshape the staff around him.

It is also worth noting what the report does not resolve: the degree to which the staff's two-year struggles reflect coaching, personnel, or the particular misfortune of losing Corbin Burnes to injury for most of that stretch, watching A.J. Puk and Justin Martinez spend large portions of 2025-26 rehabbing elbow surgeries, and seeing Merrill Kelly and Zac Gallen turn in the worst seasons of their careers. The next pitching coach will inherit a staff that has real pieces — and a set of open questions that no hire alone will answer.

What to watch

The search for Kaplan's replacement is the immediate item. What the report gives us is a vacancy and a mandate to look elsewhere — the shape of the search, and the profile Arizona targets, remains entirely unaddressed by the reporting.

Beyond the staff search, the broader question is how the pitching roster itself changes. Eduardo Rodriguez and Brandon Pfaadt had solid seasons despite middling strikeout rates, per the report. Michael Soroka delivered on a $7.5MM free agent contract, with a cutter he and the team implemented in 2026 playing a meaningful role, per the report. Juan Morillo, Brandyn Garcia, and Jonathan Loáisiga provided genuine bullpen contributions. That is a workable foundation. Whether the front office adds to it — and whether a new pitching coach can coax more swing-and-miss out of a rotation that ranked 29th in strikeout rate — is the central pitching question heading into the offseason.

Lovullo declined to tip his hand on staff changes when his extension was announced. The Kaplan news answers one part of that silence. Gilbert's reporting suggests the rest of the answer is still being written.