Mariners Hire C.J. Gillman As Major-League Hitting Coach

Seattle installed a coach familiar with its farm system to address a drop in run production and speed the transition of recent prospects to the big-league roster.

Overview

The Mariners reportedly hired C.J. Gillman as their major-league hitting coach on Friday to begin a coaching-staff rebuild after the 2026 season.
Gillman served as Seattle’s minor-league hitting coordinator from 2022–25 and spent 2026 as the Washington Nationals’ director of hitting, where he is credited with organizational gains in power and plate skills.
Seattle’s offense fell from a 113 wRC+ in 2025 to a 102 wRC+ in 2026, and the club dismissed hitting coach Kevin Seitzer and manager Dan Wilson as part of a wider staff shake-up.
The team hired Gillman before naming a new manager, with Joe Espada and Jason Kanzler reported as the two finalists for that role, which leaves final staff input pending the managerial decision.
The front office expects Gillman’s familiarity with players like Cole Young, Colt Emerson, Lázaro Montes, and Michael Arroyo to help improve contact, launch angle and pitch selection and to offset likely offseason changes such as Randy Arozarena’s expected free-agent departure.