Dead Arm

Most pitchers experience this a few times in their career. My son usually lightened his work load for a few days but kept working through it.

This has happened to my son a couple of times. Both times very obvious, no radar gun needed. Both times problem with mechanics discovered after slow motion video analysis. Just take a few minutes video during a game or practice, either bring it home or have a qualified instructor critique him in slow motion. The first time this happened, my son took physical therapy for six weeks and threw lightly over the winter, working on correcting mechanics and doing shoulder specific exercises for the rotator cuff and muscles. The second time he recognized problem with mechanics early and corrected. Most important is to ensure his mechanics are sound, not throwing across his body or dragging back hip. Maybe a second opinion from a well known pitching instructor is in otder...Good luck