Colorado Rockies prospects: No. 7, JB Middleton

7. JB Middleton (409 points, 19 ballots)

Middleton became the highest-ever drafted pitcher for Southern Mississippi when the Rockies took him 45th overall in the 2025 draft (Middleton was 41st in MLB Pipeline’s draft rankings), signing the now 22-year-old right-hander to a $2.072 million bonus that was $100k under slot. Middleton doesn’t possess ideal size for a modern day hurler (he’s only 6’0”), but his repertoire includes a good three pitch mix (fastball, slider, change) that he throws for strikes. He throws from a three-quarter slot with a quick arm action, a mid-90s fastball, a late-breaking slider that gets whiffs, and a good change-up to keep lefties honest.

Middleton’s freshman year in 2023 wasn’t pretty (nine earned runs in 9 1/3 innings), but he became an important reliever in 2024 for USM, throwing 37 1/3 innings with a 4.34 ERA, 1.47 WHIP, 10.8 K/9 rate, and 6.0 BB/9 rate. Middleton’s stuff took a big step forward in 2025 and he moved into an ace starter’s role. In 16 starts, Middleton averaged nearly 6 2/3 innings per outing (105 1/3) against less acclaimed competition in the Sun Belt conference. Middleton’s 2.31 ERA, 10.4 K/9 rate, and 2.1 BB/9 rate were good, but it was his sterling 0.85 WHIP (ranking second in Division I) that was especially noteworthy.

Here’s video of Middleton in action this March with USM courtesy of Kyler Peterson, including some slo-mo looks at his delivery and release for his arsenal in the last couple minutes:

Keith Law of the Athletic ranked Middleton 8th in the system earlier this month:

Middleton is a four-pitch guy who’s up to 97 on the heater, lacking a clear out-pitch in the mix but mitigating that with plus control and a good delivery he repeats well. I noted at the draft that he was a good candidate for the Rockies, who now have their own pitching lab, to try to work with on pitch design, as his slider seems like it could be sharper and maybe become that 60 in the quiver to help him miss more bats. As is, he’s a back-end starter who should get to Double A quickly.

MLB Pipeline is more hyped about Middleton than the PuRPs electorate, ranking him 6th in the system as a 50 FV player with a 60 grade on both the fastball and slider as well as a 55 on the changeup:

Middleton works with a versatile 93-95 mph fastball that tops out at 97, showing the ability to run and sink it toward the knees or carry it up at the letters. He gets plenty of swings-and-misses in the zone, elicits lots of chases and makes it nearly impossible to lift his heater in the air. His slider is even harder to hit, combining upper-80s velocity with two-plane depth, and he’ll morph it into a cutter at times.

Middleton will also flash a plus 86-88 mph changeup that tumbles and fades and gets in-zone misses and chases like his other offerings. He has an athletic delivery, moves down the mound well and cut his walk rate in half compared to last season. His lack of physicality is the only real knock against him as a long-term starter, though his improved strikes and stuff are stronger points in his favor.

Eric Longenhagen at FanGraphs is less optimistic, grading Middleton as a 40 FV player (99th in the draft class) and ranked him 22nd in the system with a 60 future grade on the changeup:

Undersized righty who moved into Southern Miss rotation this year and held 94-95 mph heaters through well over 100 innings, touched 97 in final start of the year. Fastball lacks great life, curt upper-80s slider often looks like more of a cutter but played like a plus pitch in terms of miss in 2025. Turns over a power-tailing changeup in the mid-80s that looks more obviously plus to the eye. Will show you some pitchability elements (slider/fastball sequencing at top of zone) and was a drastically improved strike-thrower in 2025, but size and meat-of-zone locations point more toward a long relief role.

Shaun Kernahan of Three Quarter Slot wrote this about Middleton as a draft prospect:

With a short arm stroke in an up tempo delivery and super fast arm, the ball really jumps out of Middleton’s hand, but the command is quite inconsistent. He fires the ball out of a 3/4 slot and has more than enough stuff to be a factor in the professional ranks. His fastball sits 93-96 but has been up to 98 with ride and run. He snaps off a really good firm gyro slider in the upper 80s, although he can take a tick off of it and add a good amount of two plane depth at times too. His changeup sits in the mid-to-upper 80s that he throws with conviction and good arm speed and shows plenty of tumble and fade. The arm action and command to go with a bit of an undersized frame does leave plenty of reliever risk, a role he has spent the bulk of his college career in before moving to the role of starter this season. He has improved in almost every statistical category this year and really limited the number of free passes he has handed out, giving scouts much more confidence he can ultimately start long term.

Middleton has yet to make his professional debut, which isn’t surprising given the workload he had in 2025. I wouldn’t be surprised if the Rockies started him in High-A this spring after an offseason working on pitch design, though a Low-A debut is also possible. Middleton is a high-probability starting pitcher with some mid-rotation projection. That’s always a big need for the Rockies, though I’d like to see his 2025 results carry over into pro ball before I rank him where MLB Pipeline has him in the system. For me, Middleton is a 40+ FV player that I ranked ninth on my list.

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