Eight first base ideas for the Mariners
Which first basemen might the Mariners pursue in the offseason?
When the Mariners acquired Justin Turner in July, he immediately stabilized the team’s first base situation. The right-handed bat of Turner and left-handed hitting Luke Raley combined to produce a 166 wRC+ over the final two months of the season. Only Turner’s former club, Toronto (174), was better during this period.
Weighted Runs Created Plus (wRC+) quantifies how a hitter’s total offensive value compares with the league average after adjusting for park effects. League-average is always 100. Therefore, a wRC+ of 150 means a hitter was 50-percent more productive than the average player. An 80 wRC+ would be 20-percent below average.
Turner is now a free agent, which means the Mariners may be searching for another first baseman. Perhaps an everyday starter or someone to partner with Raley. With this potential opening in mind, I compiled a list of interesting candidates for your review.
Free agents and players currently under a club’s control are included. Please remember that it’s quite possible suggested trade targets may not be available. But who cares? Speculating about offseason deal-making is what makes the hot stove season fun.
Let’s begin with free agents. Please note the age listed in each table is a player’s age next season.
Pete Alonso
Selling points: Since Alonso debuted in 2019, only Aaron Judge (232) has hit more home runs than the four-time All-Star (226).
What always catches my attention with Alonso is his demonstrated ability to slug at Citi Field - one of the least favorable venues for hitters in baseball.
In 1,746 home plate appearances, Alonso has a .238 AVG/.336 OBP/.488 SLG slash-line with 103 home runs. Among players with 500 plate appearances at the ballpark in Flushing, only Yoenis Céspedes (.498) has a higher SLG than what the Polar Bear has produced. This is why I believe Alonso’s power would translate to T-Mobile Park.
The former Florida Gator played in every game this season and has appeared in 97-percent of Mets games since he broke into the majors.
Opposing pitcher handedness doesn’t affect Alonso. The two-time Home Run Derby champ has a .514 SLG against right-handed pitching and a .515 SLG versus southpaws.
Potential concerns: Strikeouts have crept up over the last two seasons.
Alonso’s Annual SO%
2021 19.9%
2022 18.7%
2023 23%
2024 24.8%
Statcast views Alonso as a poor defender with minus-9 outs above average (OAA). This placed him 36th among 40 qualified first basemen. For context, Jorge Polanco (minus-10 OAA) was the only Mariner worse than Alonso.
Outs Above Average (OAA) is a range-based metric that shows how many outs a player has saved.
Thoughts: Inking a slugging first baseman to a long-term deal as he enters his age-30 season is fraught with risk. Especially when their strikeout rate has begun to climb. Still, the possibility of Alonso thriving at T-Mobile Park does intrigue me.
Christian Walker
Selling points: Walker has been a model of consistency. This is evident once we compare his production from 2019 to 2023 to what he did this year.
Walkers’ Steady Production
(2021-23) .253 AVG/.332 OBP/.463 SLG
(2024) .251 AVG/.335 OBP/.468 SLG
Walker has won the last two National League Gold Gloves at first base and he’s a finalist for the honor this year. The graduate of Kennedy-Kenrick Catholic High School delivered the most OAA of any NL first baseman.
Potential concerns: As with Alonso, strikeouts rose for Walker in 2024. In fact, his strikeout rate was about five-percent higher than the last two seasons.
Walker’s Strikeout Rates
2021 23.8%
2022 19.6%
2023 19.3%
2024 24.1%
Thoughts: Walker hits for power, reaches base, and is a top-notch defender. But the strikeouts are concerning for a hitter well into his thirties. Then again, the Norristown, Pennsylvania native’s advanced age means he won’t command the same contract length as Alonso.
Ryan O'Hearn
Selling points: Among hitters with at least 450 plate appearances, O’Hearn’s strikeout rate was 13th-lowest in MLB and a career-best by a whopping eight-percent.
Setting aside Seattle’s in-season acquisitions - Turner, Víctor Robles, and Randy Arozarena - O’Hearn’s AVG and wRC+ would’ve been second-best on the Mariners with his OBP and SLG being top-three.
The Floridian won’t be confused for a super-utility player. But he did demonstrate some positional versatility.
O’Hearn’s Starts in 2024
1B 48
LF 5
RF 15
DH 51
Potential Concerns: O’Hearn has been primarily a platoon player. In seven big-league seasons, the left-handed hitter has 237 plate appearances against left-handed pitching. This equates to 12.2-percent of his 1,933 MLB plate appearances.
It’s also reasonable to wonder which version of O'Hearn will we see in the future. The hitter with a 25.6-percent strikeout rate through his first six big-league seasons? Or, the player at 14-percent this year?
Thoughts: O’Hearn is an interesting candidate. Still, one could argue there’s some redundancy between what the Sam Houston State product provides and what Raley delivered to Seattle in 2024.
Justin Turner
Selling points: As already noted, Turner was a major contributor after becoming a Mariner. From all accounts, the right-handed hitter was a respected clubhouse leader. More importantly, he produced at the plate.
With the Mariners, Turner started 28 games at first base and another 15 as the designated hitter. The California State Fullerton product even made a special guest appearance at his former position - third base - for one inning.
Even as he approached 40, Turner remained available. The 39-year-old played in 139 games, which was essentially his average (142) over the previous three seasons. The last 39-or-older player to appear in more games than Turner was 40-year-old Nelson Cruz (140) in 2021.
Potential concerns: Excluding 2020, Turner’s .383 SLG was at its lowest point since he was a rookie with the Mets (.334) in 2011. The former seventh round pick also produced the lowest home run tally of any 162-game season since 2014.
Oh, and he’s old by baseball standards.
Thoughts: This blogger doesn’t believe a contender should rely on a 40-year-old to be an everyday contributor. Still, Turner’s leadership and productivity could be valuable resources for the Mariners - even if it’s on a limited basis.
Carlos Santana
Selling points: Santana also demonstrated superb plate discipline with top-30 walk and strikeout rates. As a result, his OBP was better than any hitter with 400 plate appearances as a Mariner this year.
Defensively, Santana produced 14 OAA for the Twins. This led all first baseman and tied for 13th-best among all position players. Although he’s never won a Gold Glove, the Dominican Republic native is also a finalist for the hardware this year.
Santana has always been amazingly durable. Dating back to 2011, the 38-year-old has been on the IL just once and has appeared in 94-percent of his teams’ games.
Potential concerns: Santana was more productive at Target Field than he was on the road. It’s worth noting Statcast rates Minnesota’s ballpark as more favorable to hitters than pitchers.
Santana’s Home/Away Splits (2024)
Home: .248 AVG/.359 OBP/.422 SLG
Away: .229 AVG/.300 OBP/.419 SLG
A disparity in Santana’s platoon splits also exists, which has been a recurring theme for the switch-hitter in recent years. The following illustrates what he’s done against left- and right-handed pitching going back to 2021.
Santana’s Platoon Splits (2021-24)
v LHP: .276 AVG/.358 OBP/.451 SLG/125 wRC+
v RHP: .205 AVG/.306 OBP/.369 SLG/89 wRC+
Thoughts: Santana was with the Mariners in 2022 when the team made its second postseason appearance of the 21st century. So, management understands what the former All-Star brings to a clubhouse.
On the field, perhaps Santana’s premium defense makes his below-average production versus righty pitching more palatable. Then again, it’s possible a team could periodically use a left-handed batter against righties rather than the 15-year veteran. Maybe not a full-time platoon, but a part-time setup instead.
Okay, let’s turn to trade candidates. Again, no guarantee any of these players are available. I just wanted to talk about them.
Vladimir Guerrero Jr. - Blue Jays
Selling points: Guerrero was one of the best hitters in baseball with top-10 rankings in multiple categories.
Vlad’s 2024 Stats (and MLB Rankings)
44 Doubles (3rd)
30 HR (19th)
.323 AVG (2nd)
.396 OBP (3rd)
.544 SLG (9th)
.398 wOBA (6th)
165 wRC+ (6th)
Guerrero has received criticism over his physique during his career. But it’s worth noting that over the last half-decade he’s played in 696 of Toronto’s 708 games, which translates to a 98.3-percent availability rate. Furthermore, the 25-year-old was just one of eight first baseman with 100-plus competitive runs and a better-than-average sprint speed this year.
Potential concerns: Guerrero’s minus-9 OAA suggests he and Alonso were among the worst first base defenders in baseball. Only former Mariner Ty France (minus-12) was worse than the duo.
Thoughts: Yes, his glove work was suboptimal. But few hitters can mash a baseball and also demonstrate masterful command of the strike zone like Guerrero can. And, he’s only entering his age-26 season.
Ryan Mountcastle - Orioles
Selling points: If Mountcastle were a Mariner this year, his 45.2-percent hard-hit rate would’ve been fourth-best among hitters generating 200-plus batted balls with Seattle. Players ahead of him: Julio Rodríguez (48.4), Cal Raleigh (48.1), Mitch Haniger (45.9).
In 2023-24, the right-handed hitting Mountcastle boasted a .322/.375/.562 slash-line in 304 plate appearances against left-handed pitching.
Statcast rated Mountcastle as an above average first base defender and Gold Glove voters agreed. The 36th overall draft pick in 2015 is a finalist for the hardware.
Potential concerns: Mountcastle hasn’t been as impressive against right-handers with a .247/.291/.382 slash since the beginning of the 2023 campaign.
Thoughts: Perhaps Mountcastle is best suited for a platoon with a lefty bat? That said, the Paul J. Hagerty High School grad does have a career 112 wRC+. That level of production combined with excellent defense would have greatly benefited Seattle in 2024. Especially if paired with Raley.
Luis Arráez - Padres
Selling points: Arráez’s .321 AVG since the beginning of 2021 makes him one of just three hitters with 1,500 plate appearances and a .300 AVG during this period. The others: Freddie Freeman (.311), Aaron Judge (.300).
Arráez had the lowest strikeout rate among 207 hitters with 400 plate appearances. The last time a qualified hitter had a lower strikeout rate than Arráez was Juan Pierre (4.2-percent) in 2001. Before that, it was Hall of Famer Tony Gwynn (3.6-percent) three years earlier.
With the Marlins and Padres this season, Arráez started 61 games at first base and another 39 at second base. His other 47 starts were as his teams’ designated hitter.
Potential concerns: It’s a small sample. But Arráez hit just .271 at Petco Park after the Marlins traded him to the Padres in May. Is this a big deal or just the randomness of baseball?
Hard to know, although it’s a question worthy of consideration since Statcast rates San Diego’s home field depresses offenses almost to the same level as T-Mobile Park does.
Arráez was among the worst defenders in baseball this year, which is an ongoing trend since the Venezuelan debuted with the Twins in 2019. Teams have utilized him at first base, second base, third base, left field, and even a few games at shortstop as a rookie.
Thoughts: Batting average may not carry the weight it once did. But Arráez winning his third consecutive batting title with a third team is an impressive feat. That said, fans have to accept that it’s possible he’ll be a defensive liability for their favorite team.
Finally
If forced to rank the players we’ve discussed, my list would look like this:
Guerrero
Walker
Mountcastle
Alonso
Turner
Arráez
Santana
O’Hearn
Vlad is the best offensive weapon of the bunch and the youngest, too. Walker and Mountcastle both provide premium defense, which would help offset any potential offensive decline either might encounter. As for Turner, we’ve already witnessed how well he fits with Raley at first base. Why not consider doing it again?
It’s worth mentioning Yandy Díaz and LaMonte Wade Jr. were considered but didn’t make my cut.
The 33-year-old Díaz’s stats hint of a possible decline - at least they do to me. Meanwhile, Wade has struggled to remain available throughout his career. This year, he appeared in 117 games after averaging 107 contests annually over the previous three seasons.
In the near future, we can discuss the rest of the infield. We know the Mariners didn’t pick up their 2025 option on Polanco. Therefore, a need exists at second base. Plus, third base is another position in need of an upgrade this winter.
My Oh My…