Fast…very, very Mike Fast.
Smoltz’s fastball runs 91-95 mph and looks like a pretty garden-variety four-seam fastball, except for the fact, of course, that he can still get it up to 95 mph as a 40-year-old. Smoltz apparently is quite the athlete. He uses his fastball equally with lefties and righties, about 45% of his pitches.
To right-handed hitters, Smoltz features the slider prominently (44% of pitches), and he throws it in the 85-90 mph range. Lefties don’t see the slider nearly as often, only about 23% of the time.
Instead, to lefties, Smoltz works with the split-finger fastball and changeup. I had a bit of a hard time telling the two pitches apart, but the splitter seems to be thrown a little harder and with the spin axis tilted over a little more such that it has slightly more lateral and less vertical spin deflection than the changeup. The splitter runs 84-88 mph and is used almost exclusively to lefties (15% of pitches). The changeup runs 82-86 mph and is also used more to lefties (11%) than to righties (3%).
Finally, Smoltz mixes in a few curveballs in the 75-81 mph range, making up about 7% of his pitches.