The Willi Castro edition

The Mariners still need help at second base and third base. Could Willi Castro fit the bill as a starter at either position?

Ashley Landis / AP Images

While discussing a stagnant third base market, Daniel Kramer of MLB mentioned Willi Castro of the Twins as a hypothetical trade target for the Mariners. Since the hot stove is in dire need of another log to keep burning, let’s consider Castro and his potential fit with Seattle.

Selling points: Since joining the Twins in 2023, Castro’s offensive productivity has been consistent and better than what the league-average hitter delivered. The All-Star had an identical 108 wRC+ in each of the last two seasons.

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.

If Castro were a Mariner in 2024, his 31 doubles would’ve easily led the team, which was paced by Dylan Moore (23). The switch-hitter’s five triples would also have been tops in Seattle with Moore (4) finishing second again.

Castro was more effective at reaching base than most Mariners last year. Only Víctor Robles (.381), Justin Turner (.354), and Randy Arozarena (.332) were ahead of Castro on the OBP leaderboard.

We all know Moore took home the AL Gold Glove in the utility-man category. But it’s worth noting Castro was a finalist.

Castro’s Fielding Run Value of three in each of the last two seasons suggests the Puerto Rican was an above-average defender with Minnesota. Cal Raleigh (14), Julio Rodríguez (7), and Josh Rojas (6) were the only Mariners ahead of Castro in 2024.

Fielding Run Value (FRV) is Statcast's overall metric for capturing a player’s measurable defensive performance. ZERO is always average.

The highly adaptable Castro played double-digit games at five positions and even toed the mound twice last year.

Games Played (2024)

2B (40)
SS (56)
3B (27)
LF (34)
CF (30)
P (2)

Castro played in a career-high 158 games, which led Minnesota in 2024. The highest tally logged by a Mariner was 153 by Raleigh followed by Rodríguez (143).

Availability, above-average offense, and strong glove work made Castro a valuable contributor to Minnesota. The FanGraphs version of wins above replacement (fWAR) helps us gauge his overall worth.

Castro’s 3.1 fWAR ranked 64th among 207 players with 400-plus plate appearances. The only Mariners ahead of the six-year veteran were Raleigh (5.4) and Rodríguez (3.8). It’s worth noting Robles delivered the same combined value with Washington and Seattle as Castro did with Minnesota.

Potential concerns: Although he hits from both sides of the plate, Castro was noticeably less-productive when facing left-handed pitching than he was against right-handers over the last two seasons.

Castro’s Platoon Splits (2023-24)

v LHP: 292 PA/.240 AVG/.302 OBP/.356 SLG
v RHP: 752 PA/.256 AVG/.347 OBP/.411 SLG

Just to be clear, Castro’s platoon-related production isn’t necessarily a red flag. But it’s a nerd nugget worth considering as we reflect on his potential value to a lineup.

Since T-Mobile Park is arguably the least-friendly venue for run production, there’s a decent chance a player’s home and away numbers are going to be mentioned by me. In Castro’s case, he was significantly better at Target Field than on the road during his two years with the Twins.

Castro’s Home/Away Splits (2023-23)

Home: 491 PA/.266 AVG/.350 OBP/.435 SLG
Away: 553 PA/.238 AVG/.320 OBP/.361 SLG

Does this distinguishable gap in productivity matter? It could. Statcast’s Park Factors rated Minnesota’s home field fifth-best for offense, while the ballpark at the corner of Edgar & Dave was dead last.

Perhaps this is a nothing-burger, which might be explained away as a small sample. But I’m going to mention it, anyway. Castro’s offensive stats cratered over the final three months of the 2024 campaign.

Last year, Castro stole 14 bases in 23 attempts. But his overall efficiency and effectiveness lagged well behind what he accomplished in 2023 when he swiped 33 bags in 38 attempts.

Thoughts: Castro’s positional versatility and speed would benefit any big-league roster, including Seattle’s. But how his offensive productivity with the Twins, more specifically at Target Field, would translate to the Pacific Northwest is a mystery and a principal concern for this blogger.

As a Swiss Army knife, it’s easy to envision Castro helping the Mariners. But having him serve as the primary stakeholder at one position is a risky proposition - at least that’s how I see it. Doing so would risk diminishing his overall value at a time when he may be experiencing a significant home field disadvantage at the plate.

My Oh My…