Another familiar and respected figure within the Seattle Mariners’ system is officially moving on, becoming the latest organizational departure to join Stephen Vogt’s rapidly forming staff in Cleveland. In a development that reflects both the strength and depth of Seattle’s coaching talent and the growing influence of Vogt within the Guardians’ front office, longtime Mariners coach Tony Arnerich has accepted a key role with Cleveland. The Guardians announced on Thursday that Arnerich will serve as the team’s new bench coach, an important position that often operates as the manager’s closest tactical adviser and trusted daily collaborator.
Arnerich’s move ends a nine-year tenure with Seattle during which he held a variety of significant developmental and coaching responsibilities. Most recently, he spent the 2024 and 2025 seasons as the Mariners’ bullpen coach and catching instructor, working closely with both the pitching staff and Seattle’s group of catchers. His contributions were widely praised within the organization, with many crediting him for helping refine the team’s overall pitching operation and for playing a central role in the behind-the-scenes communication efforts that are vital to sustaining a strong bullpen.
The news of Arnerich’s departure came just one day after Cleveland revealed another Seattle-based hire: former Mariners assistant general manager Andy McKay. On Wednesday, the Guardians named McKay their new field coordinator, placing him in charge of overseeing instruction, player development protocols, and on-field organizational philosophy across the system. McKay spent roughly a decade in the Mariners’ front office and player development hierarchy, holding multiple titles while shaping Seattle’s minor league processes and mental skills programs.
With Arnerich and McKay both departing in back-to-back days, the Mariners have now seen two high-ranking developmental minds leave for Cleveland, joining Vogt, who himself has deep ties to Seattle. Vogt, a former MLB catcher with a long reputation for leadership and communication, worked as Seattle’s bullpen coach during the 2023 season. His ability to connect with players and staff left a strong impression on the organization, even though his Seattle tenure lasted only one year. That offseason, Vogt was hired to replace Terry Francona as the manager of the Cleveland Guardians. Since taking over, he has quickly made his mark, earning the American League Manager of the Year honors in each of his first two seasons at the helm.
Given Vogt’s Seattle background, it is unsurprising that he has shown interest in bringing aboard former Mariners colleagues whose philosophies align with his own. Both McKay and Arnerich are known for their detail-oriented approaches, emphasis on communication, and strong track records of developing talent—attributes that clearly align with Vogt’s managerial style. Cleveland has been focused on expanding and refining its internal processes, especially in the areas of player development and game preparation, making McKay and Arnerich natural fits for what the Guardians are trying to build.
Arnerich’s professional journey with the Mariners began in 2017 when he entered the organization as a dual-role hitting and catching coordinator. His early years were spent primarily at the player-development level, where he worked hands-on with young hitters and catchers throughout Seattle’s minor-league system. His first three seasons in Seattle were dedicated to technical improvement, biomechanical refinement, and the installation of consistent teaching systems across multiple affiliates. During that stretch, the Mariners made a deliberate push to overhaul their developmental infrastructure, and Arnerich became one of the key figures implementing those changes.
After establishing himself as a reliable communicator and instructor, Arnerich was promoted to minor league field coordinator and catching coordinator for the 2020 and 2021 seasons. In this expanded role, he helped oversee organizational instruction and played a central part in shaping the Mariners’ catching pipeline. He worked with prospects at every level, helping guide developing catchers through both defensive fundamentals and strategic elements such as game calling, scouting-report preparation, framing mechanics, and communication with pitchers. Seattle’s farm system saw several catchers take meaningful steps forward during those years, something that helped fuel Arnerich’s rise within the organization.
His success in the minor league system led to an opportunity on Seattle’s big-league staff. In 2022, the Mariners promoted Arnerich to the major league coaching staff, where he became one of the team’s hitting coaches. Over the course of two seasons in that position, he assisted with game planning, mechanical adjustments, and overall offensive strategy. The Mariners valued his ability to translate complex data into practical insights for players. His work during this time was widely regarded as important to Seattle’s offensive growth, particularly among younger hitters who benefitted from his instructional style.
Despite his success with the hitting group, Arnerich made another transition ahead of the 2024 season, moving into the role of bullpen coach and catching instructor. This shift reflected Seattle’s confidence in him as a versatile coach with a deep understanding of the game’s technical and strategic elements. In his bullpen role, he collaborated closely with the pitching staff, helping integrate scouting information, pitch sequencing strategies, and bullpen-day structure. As the catching instructor, he remained heavily involved in preparing Seattle’s catchers not only for defensive responsibilities but also for handling the pitching staff, an area where his background as a former professional catcher proved invaluable.
His ability to coach both pitchers and catchers made him a uniquely well-rounded contributor to Seattle’s staff. Teams rarely find individuals who can work seamlessly across multiple areas hitting, defense, pitching communication, and game strategy and Arnerich’s versatility was frequently noted by Mariners leadership. For Cleveland, adding someone with that range of skills is significant, especially as Vogt continues shaping a coaching staff that mirrors his own catcher-centric perspective on the game.
As Cleveland’s new bench coach, Arnerich will step into one of the most influential roles on a major-league staff. Bench coaches are often considered second-in-command and frequently work as the manager’s strategic partner throughout games. Responsibilities typically include assisting with in-game decisions, overseeing preparation, coordinating pre-game routines, advising on matchups, and serving as a bridge between the coaching staff and players. Given Vogt’s experience and personality, Arnerich’s ability to communicate clearly and manage multiple systems will likely be a strong asset.
For Seattle, Arnerich’s departure represents both a loss of institutional knowledge and another sign of how attractive the Mariners’ developmental and coaching processes have become to other organizations. In recent years, Seattle has built a reputation for identifying and cultivating high-level coaching talent, and the fact that multiple staff members are being hired away speaks to the strength of the organization’s internal systems. Still, it also means Seattle must continue to replenish its coaching pipeline, a challenge that often accompanies competitive, analytically inclined franchises.
Cleveland’s rapid hiring of former Mariners personnel also underscores the growing connection between the two organizations. With Vogt leading the Guardians and bringing in people he trusts and respects, Cleveland is effectively adopting portions of Seattle’s developmental DNA. Both teams have historically prioritized pitching, defense, and systematic development, but this wave of Mariners-to-Guardians moves could further align their philosophies in the years ahead.
Arnerich, now 45, brings decades of combined playing and coaching experience into his new role. Before joining Seattle, he spent time coaching at various levels, building a reputation for clear instruction, strong communication skills, and a deep understanding of catcher responsibilities. His background as a player—primarily as a catcher who spent years in the minor leagues—has consistently shaped his coaching style, giving him a perspective rooted in the challenges of preparing for each game from behind the plate.
Both he and McKay are expected to play major roles in supporting Vogt and continuing Cleveland’s recent run of success. With Vogt winning the American League Manager of the Year award each of the past two seasons, the Guardians’ organizational momentum is strong, and adding coaches familiar with his approach creates continuity that could benefit Cleveland over the long term.
In the end, Arnerich’s move represents both personal opportunity and another example of the Mariners’ growing influence on the broader baseball landscape. Seattle loses a valued coach who spent nearly a decade helping shape the organization’s identity, but Cleveland gains a trusted advisor and versatile instructor who fits perfectly into Stephen Vogt’s vision. With McKay joining him and Vogt continuing to put his stamp on the organization, the Mariners-Guardians connection remains one of the most quietly notable storylines of this offseason.
