Who Should Be Playing Third Base for the Mariners in 2020?

As the Mariners head into a shortened year two of the big rebuild, there are many questions left to be answered for the team in 2020.

One of the biggest questions is who should be getting starts at third base this season? Last season the Mariners played seven different players at third base and only four are still on the team. Kyle Seager and Dylan Moore are two of the four with the third being Shed Long, but he should be the full-time second base starter and only played one game at third his rookie season.

The fourth is Austin Nola, but he only played four games at the position last year and is expected to spend most of his time in 2020 backing up Tom Murphy at catcher. The two who are no longer in Seattle are Tim Beckham (10 games played at third) and Ryon Healy (44 Games at third), while Kristopher Negron (1 game at third) came back to the team as a front office executive.

When the 60-man player pool was announced on June 28th we found out that 16 of the 60 players are infielders, with four of them being third basemen with MLB experience. Kyle Seager obviously made the player pool, joined by second-year Mariner Dylan Moore, and newcomers Sam Haggerty and Patrick Wisdom.


Seager is heading into his tenth year in a Mariner uniform, and during his time with the team, he’s worn it better than most. In fact, he is probably the greatest third baseman in Mariners’ history. He holds a career OPS of .767 with an OPS+ of 113 (13% better than league average of 100).

Last season he had an OPS of .789 with 23 HR’s in 443 plate appearances. He’s currently fifth on the list of highest career WAR for Mariners position players at 32.8, behind Griffey, Edgar, Ichiro, and A-Rod. He’s going into year six of a seven-year deal that will pay him $19.5 million this season and $18.5 million next year. The deal also includes a team option for 2022 of $15 million that will turn into a player option if he is traded.


Moore had a disappointing rookie season and will look to build off of a strong spring. In 282 plate appearances, Moore had an OPS of .691 with an OPS+ of 88 (12% below league average). He had a WAR of 0.1 and a defensive WAR of 0.0. This spring, in limited plate appearances (15), he had a double, a homer, and an OPS of 1.400. However, Baseball Reference had his opposition quality as 6.9 (7 is AA level competition). It is also sad to say that the most memorable moment of his rookie year was his famous throw home to nobody.


Haggerty was a member of the Mets organization last season where he was able to make his MLB debut; however, he is still searching for his first major league hit after only getting just four at-bats. He also got the MLB version of coal in his stocking for Christmas when he was DFA’d by the Mets on December 24th, then the Mariners claimed him off of waivers two and a half weeks later. In limited at-bats this spring due to elbow soreness and, you know, COVID-19 shutting the league down, he raked with two doubles and a .929 OPS. Similar to Dylan Moore, he faced a Baseball Reference opposition quality of 6.8 meaning his at-bats came against an average of high A competition. I don’t see Haggerty making the initial 30-man Opening Day roster as they have too many options at third base and utility infield.


Wisdom is no longer a “prospect” at age 28 but he definitely has some potential from the right side of the plate. Wisdom has spent parts of the last two seasons with the Cardinals and the Rangers in MLB and still has rookie status because of his lack of Major League playing time. In 58 plate appearances in 2018 with St. Louis, Wisdom had four home runs and an OPS of .882. 2019 was not as kind to him as he had an OPS of .377 in only 28 MLB plate appearances.

The former first rounder’s minor league stats are really what stand out, and the Mariners will hope that his power can transfer to the bigs as he had 77 HR’s the last three seasons in AAA and his lowest OPS in that stretch was .817. Wisdom has played a lot of both first base and third in his pro career, but with Vogelbach, White, and Nola probably getting every start at first, he’ll have to fight for the backup or starting third base role to make the 30, then 28, then 26 man roster.

So now to answer the question of who should be starting at third? The answer is Moore or Wisdom. The big part of the question is who SHOULD be starting. Seager has always been one of my favorite Mariners and I want what is best for him which would be to play on a contender, and what is best for the Mariners is to give a guy who has potential and will be around for many more years, like Moore or Wisdom, regular playing time.

Seager will obviously be the starting third baseman on Opening Day and most days after, but with a delayed trade deadline on August 31st, this gives the Mariners time to hopefully see Seager have an excellent five weeks. If that happens then Seager’s big contract could potentially be worth it to a contender in need of a third baseman.

That would leave a competition between Dylan Moore and Patrick Wisdom to potentially be the third baseman of the future, with Moore being 27 and Seattle having five more years of control, while Wisdom is 28 and the Mariners still have six years of control. Both have shown sparks in the Minors, but with Wisdom’s power potential I really hope he can get regular MLB at-bats as he had in St. Louis, and be the third baseman of the rebuild.


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