Jack
Postma

RHP Jack Postma (Barrington, 2028) provided one of the highest upsides at the event with his wiry, long-limed 6-foot-3, 186-pound frame. He controlled his levers well on the mound, staying simple, and extending down the mound, paired with a loose, quick arm action out of a lower ¾ slot. His fastball worked out of the hand clean, sitting 87-89 mph throughout, playing mostly straight. He showed confidence in his changeup that worked with heavy fade (avg. 16.4” HM), sitting 77-79 mph. Postma also showed confidence to throw his curveball, sitting in the low-70s with 11/5 shape, and the ability to land for strikes (60%). The frame, current polish, and movement patterns on the mound make Postma a high-follow prospect in Illinois’ freshmen class.

RHP/1B Jack Postma (Barrington) stands out physically at 6-foot-3, 180-pounds, and he has the stuff on the mound to match. The right-hander was lights out over his four innings of work, only allowing one hit with no runs, two walks and four strikeouts. Its and easy, long-levered operation with a quick arm out front, and we’ve seen his fastball as high as 83 mph in recent looks. Not only was his arsenal impressive, but he also showed a calm and collected confidence while he was on the mound. High-ceiling arm with his best days very much still ahead of him.

Postma, presenting a lean and athletic 6-foot-3, 180-pound frame, provided multiple clutch hits with runners on base en route to the Sparks’ 12-4 win Friday night. Delivering with a two out RBI single to get the Sparks on the board and a loud two strike RBI triple to straight away centerfield, establishing a 5-4 lead at the time. Offensively, he displayed a center to right-center approach, significant plate coverage, and an advanced ability to adjust with two strikes. Mechanically, with less than two strikes, he has a short stride, quick load, slightly open stance, and toe tap for timing. With two strikes he eliminates the toe tap and stride, closes the stance, and relies more on back hip drive and hand speed. With room for additional physical development, Postma poses a big time run producing threat in the coming years. Postma also got the start in a high-leverage game against a Top Tier Iowa team that showed well this weekend. On the mound, there is a lot to love with Postma’s arm action and delivery. Outside of the clearly advanced frame, Postma’s arm gets around quickly and he works downhill with ease. The 2028 grad ran his fastball up to 82 mph while he sat 79-81 mph. He was able to land the majority of his FBs for strikes and he worked inside-out and lived on the corners. The physical right-hander also showed off a CB that sat 63-66 mph and a CH that ranged from 70-73 mph. Postma had a feel for both breaking pitches and was able to land his CB for strikes when necessary. With Postma still being years away from graduating high school, he has time to figure out how to use the frame he possesses and will only rise when he does so.

Positional Profile: RHP/1B
Body: 6-3, 180-pounds. High-waisted, long-limbed frame, projectable.
Delivery: Slow, controlled, medium leg-lift into balance point, tall/fall lower half.
Arm Action: RH. Long draw out of the glove, releases by ear.
FB: T81, 76-80 mph. Firm out of the hand, plays with some sink, heavy arm-side run at times. T1840, 1694 average rpm.
CB: 59-61 mph. Gradual 11/5 action, has feel for the zone. Got better as the 'pen went on. T1733, 1650 average rpm.
CH: 65-67 mph. Arm-side fade, lands consistently to the arm side. Best of the offspeed offerings. T1580, 1492 average rpm.