Blake

Walston

Walston underwent Tommy John surgery one year ago Thursday. The 24-year-old, who made his major league debut by posting a 4.42 ERA in 18 1/3 innings in 2024, might be a rotation candidate in the second half of the season.

Walston will miss the entire 2025 season after undergoing Tommy John surgery earlier this month. The procedural move opens up a spot on Arizona’s 40-man roster.

Walston, 23, will miss all of the 2025 season after the procedure, and there’s a good chance he’ll miss the beginning of the 2026 campaign as well. Walston is one of the more talented pitching prospects in the Arizona system despite a poor season last year, but this is obviously a significant setback.

Walston, 23, is back with the Diamondbacks moving on from Dylan Floro. The 23-year-old lefty has a chance to make a start with Arizona before the season ends, but more than likely comes up as a multi-inning reliever.

Walston missed two months with elbow inflammation. While typically a pitcher would be expected to make at least three or four rehab starts after such a lengthy absence, the Diamondbacks are activating him and demoting him after just one appearance because they don’t want to have to continue to provide a major league salary and service time to him and they especially want to be protected in case he has a setback.

Walston ascended to the majors earlier this year and has pitched well for Arizona with a 2.84 ERA, 1.42 WHIP and 11/9 K/BB ratio across 12 2/3 innings (three appearances, two starts). No word yet on how long the 22-year-old lefty will be sidelined, but he figures to miss at least a couple weeks, even in a best-case scenario.

Walston didn’t get a chance to go for his first big-league victory, as the Diamondbacks pulled him with a 4-1 lead in the fifth. To be fair, he did have two runners on base at the time. The Diamondbacks summoned Kevin Ginkel, usually more of a late-game reliever, and he stranded one of the two runners to make it 4-2. Walston has a 2.84 ERA after two starts and one relief appearance, but it’s concerning that he’s walked nine batters in 12 2/3 innings. He’ll likely get at least one more start before Zac Gallen returns.

The 22-year-old southpaw struck out four batters on the afternoon while issuing one base on balls. Walston got eight swings and misses on 65 pitches on the day — three each on his fastball and curveball — while registering a solid CSW of 29 percent. It’s unclear if this will be a one-time thing, or if the Diamondbacks will give him another start next week against the Mets in New York on Saturday. If it’s the latter, he could have some deep league appeal for his strikeout upside.

Walston is up to make the start Sunday against the Marlins. He allowed two runs over 3 2/3 innings of work in his previous appearance in the majors earlier this season. Walston has some long-term potential as a 22-year-old former first-round pick, but there’s more risk than reward in his current profile.

The 22-year-old left-hander has made just one appearance at the big league level this season, posting a 4.91 ERA, 1.91 WHIP and a 5/4 K/BB ratio over 3 2/3 innings of work. Even against the Marlins, he won’t be a recommended streaming option for fantasy purposes.