3 Diamondbacks Prospects Who Have Stumbled in 2025

As we get closer to our midseason prospect rankings update here on Arizona Diamondbacks on SI, we're highlighting players who have drastically improved their stock and those who are trending in the wrong direction. This installment will cover three players who have hurt their standing in the organization with their 2025 performance.

Both cases show that player development is rarely a smooth and linear path. It serves as a reminder that sometimes players have to struggle in order to make the necessary adjustments to reach the big leagues.

The three highlighted prospects include a former top pitching prospect who has lost the strike zone, a former No. 2 overall pick who has struggled to develop, and a pitching prospect who has gotten off to a slow start after signing for a seven-figure bonus out of college.

RHP Yilber Díaz (No. 6)

Díaz made significant progress in his ability to throw strikes in 2024, earning a major league call-up and holding his own. However, he's taken a step backward in 2025. In nine appearances between Reno and Arizona, he has completed 33 innings and has as many walks as strikeouts, with 34 apiece. In his last start, he completely lost the strike zone as he walked five of six hitters on 28 pitches before getting removed.

In addition to the command issues, the velocity on his fastball is down a tick from 96.0 MPH to 95.1 MPH. It could be a case of trying to sacrifice a little bit of velocity for more control, but for a max-effort thrower like Díaz, it's not a good sign trying to project him either as a starter or reliever.

With both his ability to throw strikes and velocity down from 2024, his bottom-line results have suffered. In Triple-A, he has a 7.50 ERA and a 6.60 FIP in eight starts. He's walked at least four hitters in each of his past five starts and there doesn't seem to be an end in sight for this recent bout of wildness.

His secondary pitches have done relatively well, as opposing hitters are batting .167 against his death ball slider and .182 against the knuckle-curve. However, if the goal is to develop him as a starter, he'll need to improve his fastball command. Otherwise, he's more of a fit for the bullpen, where he can eat innings in chunks of 2-3 per outing.

The question for Díaz is if he'll need to spend time on the Development List and go back to the complex to work on his mechanics and feel for his pitches to improve his ability to throw strikes. He won't be able to progress if he's walking four to five hitters a start and after this season he'll be down to one minor league option.

OF Druw Jones (No. 7)

The Diamondbacks took a gamble on Druw Jones' lofty offensive ceiling, but the bat just hasn't developed as intended. Some of that is due to injuries in his first two years in the system, but there are still major issues in his swing that threaten to handicap his ceiling, if not stall him out in the minors.

In 37 games, Jones is hitting .265 with seven doubles and a .670 OPS. Even accounting for the pitcher-friendly league in the Pacific Northwest, FanGraphs grades his offensive production to be 8% less than league average with a 92 wRC+. He's walking at a healthy 12.3% clip, pushing his on-base percentage to a solid .357 mark.

The two biggest issues have been his inability to turn on fastballs on the inner third of the plate for power and being vulnerable to right-on-right spin. Jones is still striking out at a 26.3% clip, but his ISO has bottomed out from .130 in 2024 with Visalia to .047 in Hillsboro. He's yet to hit a home run this season and only has eight in 815 plate appearances.

The lack of in-game power isn't a disqualifying development for Jones, who still has elite speed and can play center field better than anyone in the organization. However, that caps his ceiling as a defense-first fourth outfielder with acceptable on-base skills and can steal a base (think Jarrod Dyson). However, for a player drafted with the No. 2 overall pick, it's going to be a huge disappointment if that's the outcome.

Jones is only 21 years old, so he's still relatively young for the level and still has time to grow. But he'll need to show improvements in getting the right type of batted ball contact conducive to generating more power. His ground ball rate is 63.5%, much higher than the 57.2% rate he posted with Visalia last season. If he can fix the ground ball issues, that should help his power projection, which should improve as he gets older and adds more strength.

LHP Grayson Hitt (No. 37)

Hitt is in his first full season with the organization since recovering from April 2023 Tommy John surgery. The 23-year-old has struggled with command, as he's walked 21 and struck out 27 over 20.1 innings with Low-A Visalia. The poor command has led to long innings, short starts, and a pretty rough 7.08 ERA and a 5.90 FIP for the former college starter.

It's a continuation of the lack of control he exhibited at the Complex last season, when he walked 11 hitters in six innings. Despite a solid called strike plus whiff rate of 32.2%, he's too often trying to get back in the count and isn't in a position to use his secondary stuff to finish off hitters. That's an area that will have to improve quickly for the Diamondbacks to continue trotting him out as a starter.

Hitt features a low-90s fastball that tops out at 95 MPH and complements that with a curveball, slider, and a cutter. He's pretty much now a lottery ticket arm with a high bust risk despite signing a seven-figure bonus in the fourth round of the 2023 draft.

If the high walk rate continues, it could be in the Diamondbacks' best interest to shorten up Hitt and see if he can move quickly up the system. In terms of left-handed relievers, they only have Philip Abner and Nate Savino in the system who could project into a major league bullpen. If Hitt could regularly stay close to his top speed of 95 MPH in short bursts, he might be more valuable as a reliever long-term.