A Full Breakdown of the Philadelphia Phillies 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 Philadelphia Phillies who will be on the Surprise Saguaros this fall. The team will consist of players from the Milwaukee Brewers, Cleveland Guardians, Texas Rangers, and the Kansas City Royals.

Philadelphia Phillies:

Eiberson Castellano RHP: After multiple years of injuries mostly back spasms Castellano broke out in 2024 throwing a combined 103.2 innings between High-A and AA. He pitched to a 3.99 ERA while striking out 31.3% of batters and dropping his walk rate down to 6.7%. Before the season the Minnesota Twins actually ended up taking Castellano in the Rule 5 Draft with the hope he could keep up those numbers in Spring Training and could pitch in the Twins bullpen. He did not pitch well, walking 19.2% of batters in 10.2 innings. He was returned to the Phillies and spent the season back in AA getting off to a decent start in four games throwing to a 3.60 ERA in 15 innings but was put on the injured list and didn’t return to the AA roster for a month and after just an innings was put on the injured list again and missed another month. He spent the rest of the season pitching out of the bullpen unlike past seasons where he mostly started. He didn’t pitch well out of the bullpen to a 6.30 ERA after his return. He’s got some great stuff thrown with a four seam fastball and sinker combo that sit in the mid to high 90s. His best secondary is his curveball which sits in the low 80s and had a 49% whiff rate in 2024. He also throws a changeup that’s in the high 90s. If he’s coming out of the bullpen he should be an electric arm if he can throw strikes. 

Jack Dallas RHP: After five years at Lamar University Dallas went undrafted in the 2022 draft and was scooped up by the Phillies. He’s slowly climbed through the minors throughout the years pitching very well out of the bullpen making it to AA in 2024 and pitching the entire 2025 in the AA bullpen. He’s a reliever who’s able to go multiple innings and pitched 49.1 innings in 31 games this season to a 3.47 ERA. He gets a decent amount of strikeouts to a 23.3% rate this season and keeps his walks down to 6.7%. Dallas doesn’t have the highest velocity with his fastball only sitting around 93 mph but he has great pitch shapes on all his pitches and he has elite spin rates. He throws a slider with 15.7” of horizontal break that is his chase pitch as well as a cutter in the high 80s. Can definitely be a mid inning reliever in the big leagues. 

Jaydenn Estanista RHP: Being signed out of Curacao in 2019 Estanista has been pitching for both the Phillies minor league teams and for the Netherlands national team the past few years. He has electric stuff and has struck out hitters at a high level his entire career. In 2024 between Low-A and High-A he struck out 31.1% of batters. This season his rate dropped to 24.5% though. His biggest problem is an inconsistent release that causes him to not throw strikes often and walk a lot of batters. This year he walked 15.6%. He stands at 6’3” with great athleticism that gives him the ability to throw in the mid 90s with great ride. He also has a plus slider with great depth. Not sure what happened to his strike outs this season with two plus pitches out of the bullpen will be great to see his pitches this fall. If he can actually get command of his pitches Estanista is easily one of the top reliever prospects in the Phillies system but currently he can’t be with some of the worst command in the system. 

Daniel Harper RHP: Drafted back in the 17th round of the 2022 draft out of Kentucky Harper has climbed all the way up to AAA this season pitching out of the bullpen. In 2024 between High-A and AA he threw 51 innings to a 2.82 ERA and 3.14 FIP while striking out 29.3%. This season the plan was to start Harper back in AA but after his first appearance out of the bullpen he was put on the injured list. After making four rehab appearances in Low-A Harper returned to the AA roster in mid June. He pitched in five games and only gave up 2 hits and a walk so was immediately promoted to AA. He made four appearances before being put back on the injured list and missing a little less than a month. He pitched the rest of the season uninjured but had mixed results. In total he pitched in 15.1 innings in AAA to a 10.57 ERA. It was weird for Harper as he was either throwing blow up innings where he’d give up multiple runs or throw an inning of no runs. He even had a two game stretch where he gave up 10 runs. His walk problems that were an issue in 2023 jumped back in AAA to a 12% rate and his strikeout rate which was still high in AA this year dropped to only 17.3%. Harper doesn’t have monster stuff but his fastball sits in the mid 90s and got great chase and whiff rates in AAA but had a xwOBA con of 0.471. He struggled to throw his cutter for a strike and could rarely get any whiffs on it. He also has a high 80s changeup that has great fade but he struggled to throw for strikes and hitters laid off it. It’ll be interesting to see what changes Harper will make to get hitters out in the AFL.

Tommy McCollum RHP: A year spent between three different levels McCollum started the year in High-A and eventually made it AAA by the end of the year. After spending the entire 2024 season in AA I’m not sure why he was in High-A to start the year with no injury or anything in Spring. After a great 8 innings pitching to a 1.13 ERA he was promoted to AA where he spent most of the year throwing 45 innings to a 3.20 ERA and 2.89 FIP. He was then promoted to AAA for the end of the year and threw 2.2 bad innings. He’s got a good amount of strikeouts with a 25.5% rate this season and his walk rate dropped from 12.4% in 2024 to 6.9% this season. He has some pretty good stuff with a mid 90s fastball, a changeup in the mid 80s that has late drop, and a high 80s cutter. Could fight for a bullpen spot next Spring but is already Rule 5 eligible and teams will probably want to see more from him than just a good 45 innings this year.

Carson DeMartini 3B: The 4th round pick for the Phillies in the 2024 draft out of Virginia Tech. DeMartini had a great start to his career in High-A this season hitting .284/.402/.474 for a 162 wRC+ in 53 games before being promoted. Even with the great numbers he still struggled with contact and strikeouts which was his major problem in college, he struck out 27.9% in High-A. After the promotion he really struggled in AA only hitting .202/.291/.288 for a 69 wRC+. His contact rates went up and his strikeouts went down but so did his walks and he didn’t hit for any power. DeMartini has shown plus raw power with some high exit velocities on pitches on the inner plate but didn’t show it at all in AA. Even with not showing top of the line speed he stole 45 bases this year and showed great knowledge of pitcher timing. He mostly played third base this season but had a few games at shortstop and 3 at second in 2024. Surprisingly he looked great defensively this season at third which was seen as a negative of him in college. 

Aidan Miller SS: The top Phillies prospect continued to excel this season as he reached the upper levels of the minors. Being drafted with the 27th overall pick out of high school in 2023 he rose through 3 levels in his first full season in 2024 hitting .261/.366/.446 for a 133 wRC+ between Low-A, High-A, and 5 games in AA. This season he spent most of his time in AA playing 108 games hitting .250/.382/.427 for a 134 wRC+ with 13 homers, 25 doubles, and 52 steals. He was promoted to AAA for the end of the season and in only 8 games really impressed. He hit .333/.514/.519 for a 184 wRC+ with a homer and stole 7 bases. Miller has big raw power for a 21 year old shortstop and has improved on a questionable hit tool this season making contact on 77.1% of swings. He also showed his patience at the plate, only swinging at 39.4% of total pitches he saw. Miller has super quick hands and great bat that are able to lift the ball well he had a 36.9% flyball rate compared to a 39.2% groundball rate so unlike most of his peers he’s been able to pull the ball in the air well. Plus power combined with a great approach and swing creates a top prospect for any team. Coming out of high school and still in recent reports people believe Miller should move to third but all the Phillies have done is play him at shortstop so far in his career. He has a great arm and the athleticism to play the position but tends to have a slow exchange which has caused errors. With Turner at short in Philly for the near future and Miller likely making his debut next season it’ll be interesting if he gets some time at third and second this fall. 

Dante Nori CF: The 2024 first round pick for the Phillies got off to a great start this season. Nori spent most of it in Low-A playing in 109 games hitting .262/.363/.381 for a 110 wRC+. Drafted out of high school Nori has a great approach and he showed it off walking in 13% of his at bats this season while only striking out 14.7% of the time. He made great contact too with a 83% contact rate and rarely whiffing. He has some raw power hitting some balls around 100 mph exit velocity but that will have to be developed in the future. His biggest calling card even though he has elite contact skills is his speed. Maybe some of the fastest times out of the draft last season and he stole 52 bases last season. He was called up for the last 11 games of the High-A season and hit well in only 53 at bats. The Phillies wanted him to get more plate appearances so he was called up for the end of the 2025 season to AA where he struggled in only 22 at bats but figured it out in his last game going 3/4 with a triple. He’s old for being drafted out of high school at already 20 years old but with the advanced approach he could jump through the levels quickly.

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