SEATTLE -- The Mariners on Monday announced some significant changes to their coaching staff under manager Scott Servais.

Here’s a breakdown of the changes:

• Jarret DeHart, promoted to hitting coach and director of hitting strategy (previously: assistant hitting coach)
• Tony Arnerich, named hitting coach (previously: Minor League field coordinator)
• Andy McKay, named Major League coach and senior director of baseball development (previously: director of player development)
• Kristopher Negrón, named first-base coach (previously: Triple-A Tacoma manager)

Additionally, Seattle’s bench coach, Jared Sandberg, will not return, and its hitting coach, Tim Laker, declined the club’s offer to return.

And here is the rest of the 2021 staff that is returning in their same roles:

• Manny Acta, third-base coach
• Trent Blank, bullpen coach and director of pitching strategy
• Perry Hill, infield coach
• Carson Vitale, Major League field coordinator
• Pete Woodworth, pitching coach

Also, Nasusel Cabrera (batting practice pitcher) and Fleming Báez (bullpen roles) will return to the big league staff in their respective roles.

The club does not plan to designated a traditional bench coach to backfill Sandberg’s role, per Mariners president of baseball operations Jerry Dipoto.

“The combination of Manny, Perry, Andy and Carson, as well as Woody, provide Scott with a variety of voices he trusts,” Dipoto said in a text message.

• After 90-win year, Servais an AL MOY finalist

Each of the promotions are fairly significant, perhaps none more notable than McKay transitioning to the big league dugout. McKay will also still oversee the Mariners' player-development efforts, along with a title bump, though Emanuel Sifuentes, who was McKay’s assistant for the past year, will take over as director of player development.

McKay was one of Dipoto’s first hires shortly after he was named Seattle’s GM in October 2015. McKay, who was the peak performance coordinator with the Rockies for three years prior, specializes on the mental and psychological components of the game, and many of the Mariners’ mental-skills coaching tactics are by his doing. He’s worked with many of Seattle’s young core well before it reached the Majors, too -- such as Jarred Kelenic, Cal Raleigh et al -- which makes him a familiar face.

DeHart, who Seattle’s most polished hitters rave about, such as Mitch Haniger, steps into a larger role, just two years removed from serving as a roving Minor League hitting strategist for the Mariners. In that role, he often worked with the club’s big league hitters. Previously, DeHart was the hitting coach for the Arizona League Mariners, and before that, he was still playing college baseball at Tulane University.

Negrón also gets a big bump after just one season as Triple-A Tacoma’s manager, a role in which he led the Rainiers to a Triple-A West championship and was named the league’s Manager of the Year. Negrón, who retired after 11 big league seasons in 2019, joined the organization shortly after as an assistant to McKay, and he essentially oversaw the alternate training site in ’20 after the Minors season was canceled.

Arnerich spent each of the past two seasons as the club’s Minor League field coordinator and catching coordinator, having joined the club in 2017 as its assistant hitting coordinator and catching coordinator. He spent nine seasons as a college coach, including a stretch from 2007-14 as an assistant at Cal-Berkeley, where he was a part of its 2011 College World Series berth.

And he’s a refresher on the coaches that are returning:

• Acta: He returns for his fifth season as third-base coach and seventh on the staff, having served as bench coach in 2018-19.

• Blank: This is his second season as the club’s bullpen coach, third on the big league staff and fourth overall in Seattle’s organization.

• Hill: Beloved by his players, Hill is back for his fourth season as infield coach and 27th overall in the Majors, over which he’s overseen 10 Gold Glove Award winners.

• Vitale: He’s back for his third season as the Major League field coordinator, responsible for all aspects of the on-field work done in the player development department. Off the field, this year, he’s in the process of running 10 miles per day (3,650 total), for a local charity.

• Woodworth: This is his third season as pitching coach, having been promoted after 2019 when he was with Double-A Arkansas, where he was named the Texas League Coach of the Year.