Jack Martinez is a 22-year-old right-handed pitcher recently acquired by the St. Louis Cardinals from the Arizona Diamondbacks in a trade that sent third baseman Nolan Arenado and cash considerations to Arizona. Born on March 12, 2003, in Wichita Falls, Texas, Martinez was selected by the Diamondbacks in the eighth round (243rd overall) of the 2025 MLB Draft out of Arizona State University, signing for $167,326. His college journey included stints at Division III Trinity University in Texas, the University of Louisiana at Lafayette, and finally Arizona State for his senior year in 2025. Prior to the draft, he was ranked as the No. 242 prospect by Baseball America. After signing in July 2025, he was assigned to the ACL D-backs but has no recorded minor league statistics yet, as his professional debut was limited. Following the trade, he was assigned to the FCL Cardinals on January 13, 2026.
Martinez’s collegiate career spanned 75 games (28 starts), where he posted a 20-8 record with a 4.76 ERA overall. In his final season at Arizona State, he emerged as a surprise performer in the Four Corners region, drawing scout attention despite entering the draft as a mid-round talent.
Standing at 6’4″ and weighing 220 pounds, Martinez has a tall, sturdy frame that provides good leverage and downhill plane on his pitches. His build suggests durability for a starting role, though he’ll need to refine his mechanics for consistency.
Martinez features a four-pitch mix with solid velocity but room for command improvement:
- Fastball: Sits in the mid-90s, touching 97 mph. It’s his primary pitch (used about one-third of the time) with above-average velocity, but it lacks consistent command compared to his off-speed offerings.
- Slider: Thrown in the low-80s, serving as a reliable secondary pitch with good shape and potential for swing-and-miss.
- Curveball: In the upper-70s, mixed in occasionally for variety but not a dominant offering.
- Changeup: Around 80 mph, providing a solid speed differential from his fastball.
His secondaries show better strike-throwing ability than his fastball, which could be key to unlocking his potential.
In his 2025 senior season at Arizona State, Martinez made 15 starts, logging 77.1 innings with a 5.47 ERA. He demonstrated strong swing-and-miss stuff, posting an impressive 32.3% strikeout rate, but control issues persisted with a 9.7% walk rate. His overall college numbers reflect a pitcher with upside but inconsistency, particularly in limiting damage despite high strikeouts. Post-draft, he has yet to accumulate meaningful pro stats, with his brief 2025 assignment limited to rookie ball without recorded outings.
Strengths: Martinez’s size and arm strength give him a solid foundation, and his ability to generate strikeouts (evidenced by his 32.3% K-rate) highlights raw talent. His secondary pitches provide a good complement to his fastball, and scouts noted him as a “pleasant surprise” in 2025, suggesting untapped potential as he adapts to pro ball.
Weaknesses: Command is the primary concern, especially with his fastball, which he doesn’t locate as well as his off-speed pitches. This led to elevated ERAs in college and could cap his role if not addressed. He also relied less on his heater than typical for a power arm, indicating a need for better integration of his arsenal.
Martinez projects as a back-end starter or multi-inning reliever if he can refine his fastball command and build stamina. His draft position and limited pro experience suggest he’ll start in the lower minors (likely Low-A or High-A) with the Cardinals in 2026. With improvements, he could reach the majors by 2028-2029, but he’ll need to prove consistency against pro hitters. As a recent trade acquisition, he adds depth to St. Louis’s pitching pipeline, though he’s not currently ranked among top prospects.
