Easy tempo, easy arm action. Some wind-up. Three-quarters slot. Athletic on the mound and repeats well, but will add a bit of effort to reach top velocity. 1.3-1.4 out of the stretch and maintains velocity there.
Binghamton Mets (AA, Mets)
50: no. 4 starter
Heavy sinking fastball, worm-burner. At 89-91, it gets late downward bite that can get swings-and-misses. At 91-93 it loses some plane but still gets some armside run. Struggled at times with commanding it armside, but also got squeezed on that side of the plate. Can work both sides of the plate down in the zone with it when he is at his best.
Has only been throwing it for a few months, but it will already flash plus. Shape can vary. The best ones were 83-85 with late, hard tilt. At higher velocity, looks more like a Warthen slider, with more depth than run. Can start it in the zone consistently, but struggles to spot it to the outside corner for strikes. Could be convinced to go future 6 with another look in better weather given how fast it has developed already.
Gsellman has remarked about how developing a slider has helped his curveball, but the results are mixed. Slider and curve bled together early in his outing, became more distinct pitches later. The curve gets flatter and slurvy in the low 80s, but shows more true 11-5 break in the upper 70s. Can bury or spot. Would flash plus to the backfoot against lefties, but he falls in love with trying to backdoor it for strikes at time. Command isn't all the way there, but potential above-average offering.
Clear fourth pitch, though he threw it a lot to a lefty-heavy New Hampshire lineup. Flashes average with good sink, but struggles to get it to the outer half of the plate, will lose it out of his hand and miss armside. Show-me pitch at present, but enough feel to project a useable, if below-average major league offering.
Gsellman is your prototypical, durable mid-rotation pitching prospect. He offers a full four-pitch mix with a potential plus fastball (due to the movement and command) two breaking balls that project as above-average. The change-up needs further refinement, and he will never have a huge margin for error given the fastball velocity, but the addition of the slider in 2016 has given him a potential major league out pitch and bumped the profile a half grade. Could also fall back as a sinker/slider setup type if the profile stagnates, but I like him as a starter.