An off-speed pitch is a pitch that is not thrown with full velocity (i.e. not a fastball or slider). Off-speed pitches include breaking pitches, but also change-ups and even "trick pitches" like the knuckleball or the eephus pitch. Most pitchers, unless they have a superlative fastball, must be able to throw at least one type of off-speed pitch consistently for a strike in order to have success in the major leagues.
Pitchers who throw almost exclusively off-speed pitches are known, somewhat derisively, as "junkballers".
- Matt Kelly: "Speed limit? Baseball's slowest pitches: Looking back at the most befuddling eephuses, screwballs and more", mlb.com, June 21, 2020.