3 Non-Obvious Players the Mariners Should Keep for 2024

It's no secret that players like Julio Rodriguez, George Kirby, and Luis Castillo are the future of the Seattle Mariners organization. They're under team control for the next few years and have already made incredible contributions to the team. However, who are some of the other pieces the front office is likely holding off from the trade market?

#1 Logan Gilbert

In his third full season with Seattle, Gilbert performed reliably well in the team's third spot in the rotation. He posted a 3.73 ERA and 1.08 WHIP over 190 ²⁄₃ innings, largely depending on above-average velocity, exceptional control, and a devastating selection of breaking balls to leave opposing batters dazed and confused at the plate.

While it was lackluster in the first two years of his career, his slider became one of the best pitches in baseball in 2023. He recorded a whiff rate of 32.2% over an astounding 867 pitches and accumulated a run value of 15. The only other pitch with a lower xwOBA was his splitter, a new addition to his already diverse toolkit. Choosing to use it as his new off-speed option, his splitter had the highest strikeout rate (46.3%), whiff rate (34.7%), put-away rate (24.9%), and the lowest xwOBA (.188) out of all of his pitches.

The main driver behind the slight dip in ERA from 2022 was his tendency to give up hard contact on his four-seam fastball. He had an xSLG of .505 against the pitch and his average exit velocity (90.5 mph, 12th percentile) and hard-hit rate (44.6%, 11th percentile) left a bit to be desired. It was a strange deviation from the norm as his four-seam fastball had been his best pitch by far for the past two seasons but was otherwise average in 2023.

At just 26 years old, Gilbert would be a valuable starter for any team to have. With great durability combined with a career 3.76 ERA over nearly 500 innings pitched, there are a plethora of teams that would be happy to trade a handful of prospects and current major-leaguers to get ahold of him, especially since he won't hit free agency until 2028.

With a lack of affordable and truly effective position players on the free agent market this year, the Mariners will have to, once again, depend on their outstanding pitching and defense to win games. Although their OPS of .734 was 16th in MLB, the combined starter ERA of 3.89 allowed them to remain postseason competitors until the last week of the season. Gilbert was a big part of this and with a lack of starting pitching prospect depth, he might not be so easy to replace.

#3 Justin Topa

After pitching a total of just 18 innings over three major league seasons with the Milwaukee Brewers, Topa was traded to Seattle in exchange for pitching prospect Joseph Hernandez. In his first full season, he was stellar out of the bullpen, recording a 2.61 ERA and 1.15 WHIP over 69 innings pitched.

Choosing soft contact over pure power, Topa's strikeout rate of just 21.9% was below league-average, but his ground-ball rate of 57.4% was in the top 6% of the league. This helped him post an opposing batter barrel rate of just 3.0%, better than 97% of MLB pitchers. That being said, he wasn't unwilling to paint the edges of the strike zone when necessary.

Because of his unusually low strikeout rates for a high-leverage reliever, the name Justin Topa didn't exactly jump out to most people as one of the best bullpen arms in baseball. As with most contact pitchers, it can be hard to say whether he "just got lucky" this year or if his success was due to intrinsically good pitching. However, his xERA of 2.97 shows that the numbers on paper were pretty much deserved. Additionally, while his whiff and chase rates are in the bottom quartile, his walk rate of just 6.5% means batters will have to go down looking or try their hand at avoiding one of his patented ground balls.

Because of this year's stellar infield defense, his pitching synergized extremely well with Seattle and may not find the same results with less defensively-focused teams. Mariners relievers combined for an ERA of 3.48, fourth-best in MLB, thanks in no small part to Topa. He won't be a free agent until 2027, so despite his stock being higher than ever before, it's important that the team holds onto him if they want to repeat their bullpen success from 2023.