Casey Fossum-skinny frame; long legs, high waist, flat backside, thin shoulders don’t have a ton of room to carry bulk muscle; starts tall with a slight hunch, feet close together on the third-base side with slight orientation to first-base side; modest rock, stays vertical into high leg kick; tucks front leg close to body at apex, swings down and forward to foot strike to generate good rhythm and momentum; hands rise to head and fall with front leg; foot strike can be inconsistent, will throw across-body with some slingshot to arm action; high three-quarter release, good length, strong extension, some deception; balanced follow-through, gets over his front side consistently with a clean finish; long leg swing around plant leg, will fall off to third-base side when he over-rotates and end up in poor fielding position; elastic motion with good balance and ability to repeat despite length.
Fringe-average velocity, only cracked 90 once on an angry pitch; will show above-average movement with good tailing action; velocity can play up a tick thanks to extension at release and modest deception; plus control, command inconsistent in this start, grabbed too much white; mechanics suggest command has plus potential; not a bat-misser, hitters can adjust second time through, needs strong command to make it work; pitch plays up from raw material at present, limited projection without velocity uptick.
Above-average feel, plus movement with tumble off fastball plane; north-south action, moderate fade; long fingers generate clean release, velo separation; maintains arm speed well, consistently gets on top and turns it over, only lost a couple to the arm-side.
Below-average bite and depth, round shape at present; long wrists, struggles to snap pitch with authority; limited swing-and-miss potential, hitters seem to pick it up well; commands pitch well below the zone, will front door to steal a strike.
Overton will be an interesting nature versus nurture test case. His body is not one that’s typically built to last 200 innings a year, and his velocity a couple years after Tommy John surgery still isn’t anywhere close to some pre-injury reports I’ve seen. The natural stuff adds up to a fringe-average package highlighted by what projects to be an excellent change-up with good drop and an advanced feel for consistent execution. But he’s developed a loose, repeatable delivery that utilizes his positive assets (length and flexibility) well, and he gets around at least some of the limited strength by generating strong downhill momentum with a rhythmic pendulum push off the rubber.
There’s an intelligence evident in his approach, but his size and average fastball leave him little margin for error as he develops. His breaking ball’s lack of projection makes it tough to project a useful bullpen niche as a fallback. He’ll need to be able to consistently work off 60 or better command if he’s going to have a shot as a starter, and while the mechanics suggest that’s not an impossible or even unlikely outcome, it’s also a volatile profile with a ceiling limited to the back end of a rotation. The ingredients of a command/control southpaw are here, but there's a higher degree of risk than your typical "polished" college arm.