A cutter sits 3–5 mph slower than a four-seamer (88–93 mph) and breaks 6–12 inches glove-side late. Less movement than a slider, so batters often read it as a fastball until it's too late.
Mariano Rivera built a Hall of Fame career on his cutter alone. Yu Darvish and Yoshinobu Yamamoto have leaned on it more each year as a complement that suppresses four-seam BABIP.
Koji Uehara also worked the cutter to limit hard contact. Cutters tend to produce weak contact off the end or handle, keeping Hard-Hit% low.
Statcast tags it FC. The spin axis tilts slightly off a four-seamer's, and lower spin efficiency creates the horizontal break. Stuff+ models often grade cutters as average; they shine in Location+.
→ Related: 4-Seam Fastball / Slider / Stuff+ & Location+