Diamondbacks left-handerBlake Walston will undergo Tommy John surgery, manager Torey Lovullo tellsAlex Weiner of Arizona Sports. The southpaw will therefore miss the entire 2025 season and likely a decent chunk of 2026 as well.

Walston, 24 in June, was the 26th overall pick of the 2019 draft. His results as a minor league have been mixed. By the end of 2022, he had climbed as high as Double-A. Overall, he had 230 2/3 innings under his belt. He had a 4.25 earned run average, 27.7% strikeout rate and 8.3% walk rate.

In 2023, he was promoted to the Triple-A Reno Aces, a club that plays in the hitter-friendly Pacific Coast League. He has since tossed 214 1/3 innings at that level with a 4.62 ERA, 17.9% strikeout rate and 12.9% walk rate. He also made his major league debut in 2024, posting a 4.42 ERA in 18 1/3 innings. He spent a little over two months on the injured list due to left elbow inflammation, perhaps an omen for today’s news.

Walston’s surgery is obviously not great for his development. As a former first-round pick and notable prospect in the system, spending a year on the shelf is a lost opportunity, when he would ideally be continuing to refine his craft.

For the Diamondbacks and their pitching depth, they’re probably not so worried about the short term. Their current rotation mix is loaded. They have seven viable rotation candidates inCorbin Burnes,Zac Gallen,Merrill Kelly,Eduardo Rodríguez,Brandon Pfaadt,Jordan Montgomery andRyne Nelson. A few injuries throughout the season are inevitable but the Snakes also haveDrey Jameson,Cristian Mena,Yilber Díaz,Tommy Henry andJoe Elbis on the 40-man roster.

But Gallen, Montgomery and Kelly are each slated for free agency at the end of this season. Burnes has an opt-out chance after 2026. Rodriguez is only guaranteed through 2027. The club is surely hoping that some of their younger pitchers step up and get themselves in position to take over those jobs down the road. But in Walston’s case, he’ll be on ice for a year-plus. Once he’s healthy, he’ll then have to play catch-up and get himself back into the mix.