A Full Breakdown of the Arizona Diamondbacks prospects headed to the Arizona Fall League

The Arizona Fall League rosters have been released this week with a lot of intriguing prospects on each team. There are six teams full of prospects from Major League teams that will play starting October 6th. I’ll be writing an article and making Twitter posts about each team’s roster. This will cover the prospects from the Arizona Diamondbacks who will be on the Salt River Rafters this fall. The team will consist of players from the Los Angeles Angels, Pittsburgh Pirates, Boston Red Sox, and Colorado Rockies as well.

Arizona Diamondbacks:

Kyle Amendt RHP: One of the most unique relievers in the minor leagues, Amendt has a very over the top delivery that’s able to hide the ball super well. He was drafted in the 9th round of the 2023 draft and in his first full season in 2024 he shot up from High-A to AAA quickly. He ended the year with a 2.86 ERA between the levels striking out 40.3% of batters and walking 12.9%. He started the 2025 season in AA again and got off to a hot start with a 3.66 ERA striking out 28 batters in 19.2 innings before being put on the injured list in late May. He made his return on August 29th and pitched 10 innings in the last month of the season to a 1.80 ERA with 14 strikeouts. He still has walk troubles with a 14.4% walk rate but his unique ability to get strikeouts even with only throwing in the low 90s makes him very valuable. He throws his fastball more than half the time and it has 16.5 inches of induced vertical break and some natural cut which made it get whiffs on 34.1% of swings this season. He throws a slider that he’s able to throw for a strike really well. His best secondary though is a curveball with 10 inches of vertical break that gets a 39.6% whiff rate. One of the craziest relievers in the minors and will look to continue his success this fall and hopefully ride it into competing for a Major League spot next spring.

Yordin Chalas RHP: The Diamondbacks have been aggressively moving Chalas through the minors every season. He started in the Dominican Summer League in 2023 and was quickly moved to the states and pitched in the Complex League. In 2024 he started the season in Low-A and got out to a hot start pitching 22.2 innings to a 3.18 ERA and 34% strikeout rate. He was promoted to High-A and pitched about the same in 28 innings pitching to a 4.82 ERA and a 30.7% strikeout rate. This season he started again in High-A and has looked much worse as the Diamondbacks have been trying to transition him into a starter role. In 21 outings he threw 65 innings to a 5.54 ERA. His strikeout rate dropped to 21.4% while his walk rate stayed around his career average at 10.2%. He went back to the bullpen after a short injury list stint and pitched 6.1 innings to a 0.00 ERA while striking out 8. He was then moved up to AA where he has struggled throwing 6.1 innings to a 11.37 ERA. He’s not striking batters out and is walking 23% of the batters he’s faced. I’m interested to get some data on him this fall to see what’s been going wrong. In past seasons Chalas had one of the best fastballs in the organization that would consistently sit in the upper 90s. He also threw a slider that was still being worked on and sat in the mid to low 80s but struggled to get left handed hitters out. He’s been trying to work on a splitter but it hasn’t gone well this season. Still a very high ceiling prospect. 

David Hagaman RHP: Drafted in the 4th round in last year’s draft by the Rangers Hagaman was traded at this year’s deadline for Merrill Kelly and has barely pitched this year. He’s been recovering from an elbow surgery he had a few months before the draft and was able to make 8 starts between the Rangers Complex League and Low-A and made 5 starts after being traded to the Diamondbacks organization in High-A. In the 42.1 innings he threw to a 2.98 ERA striking out 33.7% of batters. His main problem in college at West Virginia was control but this season he only walked 6.1% of batters and only 5.3% in his 5 games in High-A. He has a great fastball that has sat in the mid to low 90s in his starts but got up to 98 mph in college. His best pitch is a tight slider in the mid 80s that got big whiffs this season. He’s also thrown a mid 80s changeup that has good fade and has flashed as another plus pitch. Standing at 6’4” and still having a lot of development ahead I would guess he can use his athleticism to get even more velocity and become a great starter. Will be a very fun arm to watch this fall. 

Drey Jameson RHP: One of the only players in the AFL with MLB experience Jameson made 4 starts in 2022 for the Diamondbacks and pitched in 15 games for 40.2 innings in 2023 but was shut down for the and underwent Tommy John surgery and missed the rest of the season and the entire 2024 season. This season he made his long awaited return pitching great in spring and pitching 3 innings for the Diamondbacks after starting the season in AAA. He was sent back down to AAA and continued to pitch until mid May where he was put on the injured list with elbow inflammation in the same one he had Tommy John surgery on. He tried to make two rehab outings in the Complex League in late June but was put back on the injured list and didn’t pitch for the rest of the season. Jameson has a great pitch mix with his fastball that sits in the high 90s and has touched 101 mph. It doesn’t have great shape and can get hit hard at times but he’s able to throw it for a strike. He also throws a sinker that sits around 96 mph with 15 inches of horizontal break. His two secondaries, a slider and changeup, are his best pitches. His slider sits around 87 mph with great movement and spin. This season in 12.2 innings at AAA it had a 40% chase rate and 49% whiff rate. His changeup sits around 90 mph with 14.6 inches of horizontal break. It had a 52.9% whiff rate this season. During spring training I thought Jameson would pitch some big innings for the Diamondbacks this season and believe he likely will next season especially if he gets back to his usual arm talent this fall and next spring.

Jacob Steinmetz RHP: After being drafted in the 3rd round of the 2021 draft Steinmetz has very slowly climbed the ranks of the minor leagues he spent the 2023 and 2024 season mostly in Low-A where he really struggled in 2023 with a 6.19 ERA but stepped up in 2024 with a 3.60 ERA. He was promoted in the middle of the 2024 season to High-A and pitched 57.2 innings to a 4.37 ERA. He significantly cut his walk rate down in 2024 and upped his strikeout rate to 23.8%. He has not pitched at all in 2025 with an undisclosed injury. Steinmetz doesn’t have great stuff, mostly throwing a slider and curveball combo that get a good amount of chase when they’re commanded well. His fastball is below average and so is his changeup. If he can keep the command he found in 2024 then he has the potential to be a starter in the back end of the rotation and stay in the league for a while. 

Kenny Castillo C: Starting the season on the injured list with an undisclosed injury he made his High-A debut in June. He struggled this season at the plate before his season ended early with another injury at the end of August. In 64 games he slashed .222/.267/.348 for a 64 wRC+. He swings often at 55.5% of pitches but makes good contact. He also chases pitches a lot and led to him having a 20.7% strikeout rate. His bat though isn’t what he’s known for as he’s a great receiver and framer. His arm and ability to throw runners out is right around average and he currently is a below average blocker but his ability to frame is some of the best in the Diamondbacks system. He’l look to work on his defense this fall with older pitchers.

Jansel Luis INF: One of the higher ceiling prospects in the Diamondbacks system, the 6’0” switch hitter only turned 20 years old before getting into High-A this season. He hit .304/.342/.422 for a 106 wRC+ this season and cut down his strikeouts by 4% to 16.3%. This was due to his increase in contact especially in the zone cutting down on his whiff rate. He was still swinging often and chasing but his ability to move his bat around the zone from both sides led to him making contact on 71% of swings outside the zone. He also showed off his above average speed with 22 stolen bases. Everything with Luis is still projecting as he hasn’t shown great raw power so far but the expectation is he had to his 170 lbs currently with 10-20 more pounds of muscle and bulk up to hit the ball harder. His big bat speed shows he has more than he’s currently shown as he only hit 5 homers this season. He’s moved all around the infield throughout his career spending most of this season at second base but also some time at shortstop and third base. He missed most of June with an injury and is looking to get more at bats this season especially against older talent. 

Jack Hurley CF: An absolutely disastrous season for Hurley as he made his AA debut and hit .218/.273/.370 for a 63 wRC+. Not awful numbers but his strikeout rate which had been a concern in his past seasons at the lower levels jumped up to 41% in AA. He also dropped his walk rate to the worst of his career 5.4%. Hurley has always had a bad hit tool with very low contact percentages but this season was the worst of his career at only 60.1% of swings he made contact while swinging at 55% of pitches. He has a tendency to swing through a lot of pitches in the zone with only a 66.1% contact rate in the zone while chasing 46% of pitches out of the zone. He has shown pretty average raw power and stole 14 bases in 2024 but only stole 1 this season. He has pretty good defense at all outfield positions and a big arm which led to him mostly playing center field the last two seasons. He has to figure out his contact problems to be a prospect and have any floor.

Thank you for reading for shorter breakdowns check out my Twitter @drew-durstock. Each day I'll release a new team's prospect breakdown.