What to Watch for Diamondbacks Prospects in the Arizona Fall League
Here's a primer on what I'd like to see from the eight players in the Arizona Fall League.
The season opener for the Salt River Rafters begins Tuesday. Eight players in the Diamondbacks organization are expected to compete over the next six weeks. It will be an opportunity for all eight players to replace lost reps. In turn, that should add more clarity to the organization on what their future plans for them should be.
Here's a primer on what I'd like to see from the eight players in the Arizona Fall League.
Drey Jameson Needs to Show Good Health
This is more or less a glorified rehab assignment for Drey Jameson. The 28-year-old fireballer needs to throw the ball cleanly and without pain. His fastball averaged over 98 MPH during the regular season, so we have a baseline to compare. He'll need to sit in that upper-90s range, with the occasional 100+ MPH reading.
More important than the velocity will be the command. With less rise than a typical fastball, he'll have to rely on locating it at the top of the zone for swings and misses. Jameson can also use his mid-90s sinker, which is better suited to attack hitters in the zone than his four-seamer. Establishing the ball-to-strike tunnel glove-side (back door to RHH, front door to LHH) will help set up his slider.
The slider is still Jameson's best swing-and-miss weapon. The pitch generated a 49.0% whiff rate and 37.8% putaway rate (two-strike pitches that result in a strikeout) in Triple-A. It should play well against most of the hitters in the fall league, who haven't necessarily dealt with Jameson's velocity or stuff.
The changeup is an interesting pitch to keep an eye on. It's a pitch he's never really mastered much in his career, but could give a different look to lefties. For now, it's not necessary to establish himself as a big league reliever. But it's something on the back of my mind to monitor, as it could determine his viability as a back-end arm.
Kyle Amendt Needs to Work the Lines
Amendt's north-south game on the mound plays up when he's locating on the top and bottom lines of the zone. He'll attack hitters with rising fastballs (19.4" induced vertical break) on the top line and big-breaking curveballs for swing-and-miss on the bottom line.
Ideally, he shows better strike-throwing ability than he has in Reno so far. In 2024, he finished with a walk rate over 20%. He looked strong at the start of 2025, looking like a midseason call-up candidate until a shoulder injury slowed him down. The Fall League will serve as a chance to make up another 10 innings and get him around 35-40 on the year.
The 6'5" right-hander will be among the organization's likely non-roster invitees in camp. While he's probably on the outside looking in for a bullpen spot, he still has the potential to change that with his performance. He's on a short list of early-season call-up candidates for next season.
Kyle Amendt Eyes D-backs Bullpen in Arizona Fall League Return
Does David Hagaman Have Frontline Starter Stuff?
For Hagaman, it's just gaining more reps and seeing how his stuff interacts with the big league ball. He got excellent results in High-A to close out the season after returning from elbow surgery.
How his stuff plays at this level will impact how quickly the D-backs advance Hagaman through the system. Five strong starts is not a strong enough sample size to suggest a promotion to Double-A.
I'll be monitoring his 4-seamer, slider, and changeup metrics on Statcast, so I can better project his stuff in a big league starter role. Right now I'd project him more as a No. 3 starter.
David Hagaman Aims to End 2025 Strong in Arizona Fall League
How Well Does Jansel Luis Square Up the Ball?
Luis is the best position player prospect from the D-backs system. He enjoyed a pretty solid year with Hillsboro, but missed three weeks with an injury.
The switch-hitting middle infielder naturally draws Ketel Marte comps due to his projectable body and growing power. While his tools aren't as loud as the D-backs' All-Star second baseman, he still carries the upside of at least an average regular.
The exit velocity metrics will be the bigger determinant. Is he hitting the ball hard and lifting it in the air? Those metrics will better determine his power output than his home run totals in the minors.
Also where he plays defensively will be interesting. He should get close to everyday reps. From what I saw on media day, he was getting reps at third alongside Braylen Wimmer of the Rockies.
Yordin Chalas Can't Be Fastball-Reliant
Chalas can hit the upper 90s with his 4-seamer. However, big league hitters can, to use a popular Torey Lovulloism, "Put wood on a bullet". How his slider and splinker, which is more of a splitter, play will be critical.
Chalas spent the year in a starter role to accelerate his pitch development in 2025. That gave him 3-4 innings plus a bullpen session a week, allowing the organization to better script his appearances. Once he was promoted to Double-A Amarillo, he went back to a traditional reliever role.
I'd like to see more swing-and-miss (9.7% swinging strike rate) in the fall league from the lanky right-hander. Using his fastball to set up his secondaries and vice versa. A strong showing accelerates his potential debut to late 2026.
What's Jacob Steinmetz's Upside as a Reliever?
At this point, the D-backs are not going to get a good return on investment on Steinmetz as a starting pitcher. His Rule 5 clock starts this offseason, and he missed the entire season with an injury.
The good news is the 6'6" right-hander will have a chance to show what his stuff looks like in the Arizona Fall League. He was mid-90s as a starting pitcher prospect, so perhaps he may see a velo bump pitching in short relief. He also features a curveball and a slider.
If the stuff looks good, Steinmetz has a chance to rocket up the system as a full-time reliever in 2026. If he's hitting upper-90s with the fastball, he has a decent chance to develop into a key bullpen piece for 2027 and beyond.
Can Jack Hurley Put His Strikeout Issues Behind Him?
Strikeouts were a major problem in Hurley's 2025 campaign. He struck out in 41.0% of his plate appearances with Double-A Amarillo, leading to a stint on the Development List. He finished out the year with Amarillo, but put up a pedestrian .207/.271/.346 slash (63 wRC+).
He's made some significant changes to his swing mechanics. He's dropped the big leg kick that he had in college and his first year in the system. He's using a more simplified motion. I'll try to learn more behind the change.
In a crowded outfield situation, Hurley is going to have to show he can stick. He's carries more defensive and baserunning value than Gavin Conticello as a fourth outfielder. The latter is a corner outfielder only, whereas Hurley is a center field option.
It will be important for Hurley to show he can not only make contact but also drive the ball to the gaps and put his speed to use. Otherwise, he's going to get buried on the organizational depth chart by Druw Jones and Slade Caldwell next season.
What Does Kenny Castillo Offer?
Castillo is mostly organizational filler behind the plate. Arizona's catching prospect depth is either young or lacks upside. Christian Cerda is a couple years away from big league action. Ivan Luciano and Carlos Virahonda just reached a full-season affiliate late in 2025.
It will be interesting to see how he handles himself at and behind the plate. He hasn't put up much offense in his minor league career, so his route to the big leagues will have to be through defense.