A career reliever with 4 surgeries.
Released by the A’s.
No affiliate offers after Pro Day. Months later: career-high 98 mph + Mets contract straight to AAA. The exact process that got Jack Weisenburger there 🧵
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@jackweis13
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Jack spent 6 years in the A’s system as a reliever. Four surgeries. Limited innings. Released in spring training 2025. His next move was smart: Go to indy ball as a 𝐬𝐭𝐚𝐫𝐭𝐞𝐫. That’s actually where I first saw him, before I was his coach
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Background + the real problem.
Career reliever, velocity had dipped after the surgeries. He knew the fastest way back was proving he was healthy by throwing hard. Signed with Tread and had January's Pro Day in mind. Focus: velocity to prove health.
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The mechanical flaw holding him back (and stressing the elbow for years). At peak leg lift he moved backward before going forward → excessive counter-rotation → pushy back leg → draggy arm action. Classic stress pattern for a guy with his injury history.
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His arm itself was elite — “that arm just works.”
Clean the delivery and there was clearly more velo available. Early focus: drills to stop the arm getting stuck behind and reduce the excessive counter-rotation.
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Pro Day. First time meeting Jack in person. During warm-up shuffles he was already 96–97… but he was bleeding through the rotation instead of stopping it. My simple cue:
“If you just rotate a little bit, you’d probably throw this 100.” Next shuffle: 99 mph.
Aug 7, 2026 · 6:26 PM UTC
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Pro Day itself was solid (94–96). Showed health. No affiliate offers came :( Right after, we deloaded, then attacked the rotational piece hard with “connected throws” (keep the back foot on the ground). This stopped the leap and forced pure rotation. Jack’s feedback: “I never felt like I was rotating this hard in my entire life.” First bullpen after the deload: 98 mph - career high! (first PR since March 2021, four surgeries in between).
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