Although they have not thrown an MLB pitch in 2023, Jackson Stephens threw 2,059 pitches that were tracked by the PITCHf/x system between 2017 and 2022, all of them occuring in the MLB Regular Season. In 2022, they relied primarily on their Fourseam Fastball (94mph), Curve (77mph) and Sinker (94mph), also mixing in a Change (86mph). He also rarely threw a Slider (87mph).
In 2022, compared to other RHP:
His fourseam fastball generates a high number of swings & misses compared to other pitchers' fourseamers, has some natural sinking action, has essentially average velo and has slightly less natural movement than typical. His curve has sweeping glove-side movement and has a sharp downward bite. His sinker is a real worm killer that generates an extreme number of groundballs compared to other pitchers' sinkers, generates more whiffs/swing compared to other pitchers' sinkers and has slightly above average velo. His change has surprising cut action, dives down out of the zone, generates fewer whiffs/swing compared to other pitchers' changeups, results in many more groundballs compared to other pitchers' changeups and is slightly firmer than usual. His slider is an extreme flyball pitch compared to other pitchers' sliders, generates fewer whiffs/swing compared to other pitchers' sliders, is much harder than usual and has some two-plane movement.