Key coach from Mariners farm system leaves for job on an MLB staff

One sign of success for pro sports teams is that coaches in the organization will be hired by other teams for jobs that are a step up the ladder. The Seattle Mariners have seen their share of that coming off their American League West division title and trip to the AL Championship Series, and another instance of it came this week.

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Washington state native and former Mariners utility man Shawn O’Malley is moving to the other Washington, joining the MLB staff of the Washington Nationals as an assistant hitting coach.

O’Malley spent the past two seasons as hitting coach for the Tacoma Rainiers, the Mariners’ Triple-A affiliate. He first joined the coaching ranks in 2020 and had stints as hitting coach for two other M’s affiliates: the Single-A Modesto Nuts (2021-22) and Double-A Arkansas Travelers (2023).

There was buzz around O’Malley this year for his work in Tacoma with Dominic Canzone and Tyler Locklear, a pair of players who worked their way back to the big leagues in 2025 after time with the Rainiers.

O’Malley was named the 2025 Dave Henderson Minor League Staff Member of the Year by the Mariners after helping the Rainiers win the second half Pacific Coast League championship. Tacoma hitters finished fourth in hits (1,455), third in RBIs (885), third in walks (704) and second in on-base percentage (.375) under O’Malley this year.

Rounding out our winners, former Mariner & Rainiers hitting coach Shawn O’Malley earns the Dave Henderson Staff Member of the Year after guiding @RainiersLand to a PCL second-half title. #TridentsUp

🔗 https://t.co/ptad0AANF3 pic.twitter.com/cCFsobdvKS

— Mariners Player Development (@MsPlayerDev) September 23, 2025

O’Malley, who will turn 38 on Sunday, played 124 big league games over three seasons, including 113 with the Mariners combined between 2015 and 2016. He broke into the majors with the Los Angeles Angels in 2014.

A switch-hitting utility player, O’Malley appeared at every position in an MLB game except pitcher, catcher and first base.

Among Mariners fans, O’Malley is likely best known for his performance on Aug. 6, 2016 against the Angels. On the same night that Ken Griffey Jr. became the first player in M’s history to have his number retired by the team, O’Malley popped a go-ahead, three-run home run with two outs in the seventh inning, lifting the M’s to an important 8-6 victory in the midst of a playoff race.

The homer was O’Malley’s second in a three-day span, and the last of his three career MLB homers.

O’Malley is a Tri-Cities native who was born in Richland and was a star at Kennewick’s Southridge High School. He was a fifth-round pick out of high school by the Tampa Bay Rays in 2006.

The Mariners have also seen the departures this offseason of third base coach Kristopher Negrón, who is the new Pittsburgh Pirates bench coach, and bullpen coach Tony Arnerich, who is the new Cleveland Guardians bench coach. Additionally, M’s assistant general manager Andy McKay was hired by Cleveland to be its field coordinator.

Seattle Mariners offseason coverage

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• Morosi: Refnsyder deal signals M’s have another move coming
• The Mariners could have one of spring training’s biggest stories
• What would a Brendan Donovan trade cost Seattle Mariners?

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