Seth Martinez

He’s been called a late bloomer. I’m enthusiastic about late bloomers!

The quick view is that if he pitches the same as last season (52.2 innings with a 3.59 ERA) he will make a very positive impact on the Diamondbacks bullpen. And, as a pre-arb player, he is very affordable.

Seth Martinez’s 2024 season had two chapters.

The two chapters were:

• March/April/May. 31.1 innings with a 2.01 ERA.
• June/July/August/September. 21.1 innings with 5.91 ERA.

What changed?

He changed his mix of pitches. His percentage of 4-seam fastballs increased from 30.3% to 35.3%. The corresponding reductions were 3.6% less changeups and 1.5% less sinkers.

Did he pitch around a weak infield defense? The Astro’s infield defense was weak (negative 4 DRS) while their outfield defense was better (18 DRS). My intuition is that Seth Martinez, despite his success in April and May, changed how he pitched to reduce ground balls (46% to 33% GBP) and strike out more batters (4.3 to 8.9 K/9).

However, the changes failed as reflected beyond just a worse ERA. Less batters grounded into double plays (1 vs 8). Also, three stats got worse (HR/FB went from 8.1% to 13.8%, BABIP went from .191 to .368, and LOB% went from 83.9% to 70.1%). Although those three stats can reflect bad luck, when all three dramatically change for the worse it’s more than bad luck.

Why are the Diamondbacks a better fit?

Better Infield Defense. The Diamondbacks have a better infield defense (positive 35 DRS compares well to the negative 4 DRS of the Astros.) This better defense will encourage Seth Martinez to return to how he pitched in April and May (higher ground ball % and pitch to contact instead of going for strikeouts).

A Similar Pitcher. The Diamondbacks had great success with a similar pitcher (with low velocity fastballs), Joe Mantiply. Last season Joe Mantiply improved his ERA, BABIP, and especially his HR/FB. In September Joe Mantiply made comments that led me to jump to the conclusion (with uncertainty) that better matchups helped him (secondarily he was helped by his pitch deception and his increased confidence). I’m optimistic that the Diamondbacks could make similar improvements with Seth Martinez.

Mt. Rushmore. Seth Martinez said the best all-time pitchers for Mt. Rushmore included former Diamondback pitcher Brandon Webb!

What is great about his mindset?

He thrives in a team environment that includes great defense (the Diamondbacks value and emphasize defense), mutual trust and confidence between players, and players striving to reach their potential. His specific words follow:

“I give most the credit to the defense tonight because they made huge plays for me back there. I mean great plays actually so I think that was a major difference knowing that I have my defense back there to help me out.” — Seth Martinez

“We’re [Sun Devils] just going to stay confident in each other. And just know that each other’s out there competing.” — Seth Martinez

“We [Astros] have a very good trust together. Everybody knows the potential of each person on the team.” — Seth Martinez

Summary.

Three points:

• If Seth Martinez pitches the same as last season, he will make a very positive impact.
• Two of the reasons he could pitch better as a Diamondback are better infield defense and better matchups.
• His mindset makes him a great fit with the Diamondbacks.