D-backs Top 40 Prospects in 2024: No. 24 Blake Walston

The left-handed Walston made a successful major league debut and pitched well before an elbow injury interrupted his season.

Arizona Diamondbacks left-hander Blake Walston (48) reacts to a called ball by the umpire as he pitches against the San Francisco Giants at Chase Field in Phoenix on Sept. 23, 2024. / Joe Rondone/The Republic / USA TODAY NETWORK via Imagn Images

This article is part of a series reviewing the seasons of the top 40 prospects still in the Arizona Diamondbacks system as of the end of 2024.

Blake Walston LHP, DOB 6/28/2001. 6'5"/175

Acquired: 1st round, 26th overall of the 2019 amateur draft

Drafted out of high school, North Carolina native Blake Walston made a slow, steady climb through the Diamondbacks system. Pitching at every level, he made it to Triple-A Reno in 2023 where he spent the entire season for the Aces.

Walston had a successful season in the hitter-friendly Pacific Coast League that year, going 12-6 with a 4.52 ERA in 30 starts, 149 innings. Despite struggling with a high walk rate, issuing 93 free passes, he learned how to pitch with traffic on the bases and limit the damage.

Walston returned to Reno to start the 2024 season, and was still struggling with walks, issuing 15 of them in his first 20 innings. But with injuries decimating the Diamondbacks rotation and bullpen, he was called up to make his major league debut on May 1.

Coming on in relief of Jordan Montgomery, he entered with a 6-0 deficit, and pitched three impressive scoreless innings, before giving up two runs in his fourth inning of work.

Related Content: Blake Walston's MLB Debut More Impressive than Final Line

Optioned back to Reno immediately after that debut, he was called up again to start on May 26. He had an excellent outing, going 4.2 innings without allowing a run, walking just one and striking out four batters.

Walston started again on June 4 at Chase Field against the Giants, and went 4.1 innings, allowing two runs. He struggled a bit with walks in that game, issuing four free passes, but he induced two ground ball double plays to limit the damage.

To that point Walston had thrown 12.2 innings, posting a 2.84 ERA and 4.27 FIP. He didn't allow a homer, but had walked nine while striking out 11. Unfortunately, two days later it was announced that Walston was placed on the 15-day IL with left elbow inflammation.

That injury kept him out for just over two months. His next game action came in AAA on August 11. He made six starts for the Aces through September 10, throwing 29.1 innings. His strikeout to walk ratio improved durng this stretch to 29/11, but he also hit five batters, en route to a 5.23 ERA.

Walston was recalled on September 15 to provide length as a long reliever in the bullpen. Ironically, he picked up his first major league win by recording just one out in relief in the top of the 10th inning in a thrilling 11-10 D-backs walk-off victory against the Brewers.

Walston's season ended on a down note however. He pitched in three more games, all losses, and gave up large crooked numbers in two of them. Over his final 5.1 innings Walston allowed eight runs, five earned.

All told, Walston pitched in 14 games for Reno and threw 65 innings with a 4.85 ERA and 5.15 FIP. In MLB he pitched in seven games, 18.1 innings, posting a 4.42 ERA and 6.17 FIP. He walked, 10, struck out 18, and allowed four homers.

2025 Outlook

Walston's rookie eligibility is still intact for 2025, thus he's grouped with the prospect list. When he was first drafted as a long, lanky teenager, it was thought he might add some velocity as he filled out. But that has not materialized. Walston averaged 91.5 MPH on his four-seam fastball at the major league level.

Despite being 6'5" tall, Walston's extension is in just the 16th percentile, registering 6.1. That's well below average. By comparison, Ryne Nelson, who is 6'3", was in the 81st percentile with 6.8 extension. Walston might benefit from a mechanics tweak that would help him increase his extension, thus allowing his fastball to play up a bit with a higher perceived velocity.

He throws five pitches, including a cutter, changeup, sweeper, and curveball. He's shown a knack for limiting hard contact and pitching out of trouble. Walston is still very young, and will be entering his age 24 season. If he can make a few minor tweaks, allowing his fastball velo to rise a tick and reduce his walks, things could suddenly click for him.

For now, Walston is a depth option, likely to start the 2025 season in Triple-A, but expect him to be called up in the case of an injury, or perhaps to provide long relief again.