Mariners Initiate Coaching Overhaul With Gillman Hire
The Seattle Mariners have hired CJ Gillman as their hitting coach, initiating a coaching restructure with the announcement of their new manager still pending. The move marks a return to Seattle for Gillman, who previously served as the team’s minor-league hitting coordinator from 2022 to 2025 before leaving to take on a role with the Washington Nationals.
Gillman takes the place of Kevin Seitzer, whose tenure with the Mariners concluded at the end of the season. The organization cited a need for change after Seitzer’s hitting approach failed to consistently resonate with the roster. During that period, the team relied heavily on home runs and walks while ranking poorly in situational hitting and contact metrics.
The hiring comes as the Mariners seek to address significant offensive struggles from the 2026 season. Seattle ranked 28th in runs scored this year, with star position players Cal Raleigh, Julio Rodriguez, and Josh Naylor all suffering career lows in several offensive metrics.
Gillman’s Impact in Washington
Before joining the Mariners, Gillman served as the director of hitting for the Washington Nationals. During his time in Washington, the Nationals ranked among the top offenses in Major League Baseball last season, scoring the third most runs in the league.
Ken Rosenthal of The Athletic reported that Gillman was intimately involved with the Nationals' minor-league side during his tenure. According to Rosenthal, Gillman helped the organization make significant gains in exit velocity, launch angle, and pitch selection while shaping a new hitting philosophy for the club.
The impact of Gillman’s work extended to the development of specific players within the Nationals system. The Washington farm system improved from 29th to eighth in weighted runs created plus (wRC+) and from 29th to seventh in home run rate during his time there.
Gillman reportedly worked specifically with prospects Lazaro Montes and Colt Emerson. Montes struggled with contact and strikeouts in 2026, while Emerson missed the rest of the season due to injury after struggling in his first year.
Addressing Organizational Disconnects
The decision to bring Gillman back to Seattle follows reports of internal issues within the Mariners' previous coaching staff. Multiple players on the Mariners told General Manager Jerry Dipoto that some organizational mantras were abandoned at the Major League level, displaying major red flags within the team's coaching structure.
Gillman’s return is expected to help bridge the gap between the minor-league development philosophy and the Major League roster. His previous role as minor-league hitting coordinator in Seattle positioned him to understand the organization's existing developmental frameworks before his departure for Washington.
The hiring of Gillman represents the first concrete step in the Mariners' coaching search process. The team has not yet announced who will serve as their next manager, leaving the broader scope of the restructure incomplete. However, the appointment of a new hitting coach signals an immediate focus on correcting the offensive deficiencies that plagued the team in 2026.
Seattle’s offensive output last season placed them near the bottom of the league rankings, highlighting the urgency of the coaching changes. With key contributors like Raleigh, Rodriguez, and Naylor underperforming relative to their career standards, the front office appears to be prioritizing a shift in hitting strategy under Gillman’s guidance.
The Mariners will now await the announcement of their new manager to complete the leadership structure for the upcoming season. Until that appointment is made, Gillman will serve as the primary architect of the team's offensive approach during the transition period.