This video diagramming Mariano Rivera's cutter is interesting viewing for any baseball fans, not just devotees of perhaps the greatest one-pitch pitcher in baseball history. (Something to shoot for, Jason Motte.) It shows what's so devastating not just about Rivera's cutter in particular but the pitch in general, which has grown more and more popular in baseball of late.
↵It even makes the distinction between Rivera's fast, tight cutter and the slower, more slider-like pitch that seems to be Dave Duncan's particular favorite. Lots of Cardinals pitchers have slowly become more and more cutter-dependent as they spend time under his tutelage; Jason Isringhausen replaced his four-seamer almost entirely as his velocity disappeared, Chris Carpenter blames his occasional home run problems this year on a cutter he can't quite locate, and even spot starter Blake Hawksworth has worked one in as his fastball velocity increases to replace his mediocre curveball.
↵But the Cardinals' current cutter champ, according to the pitch-type algorithm at Fangraphs, is Jaime Garcia. It sees the pitch he and the Cardinals call a slider as a cutter, and whatever it is he's thrown it 25% of the time this season. (Rivera throws his 87-90% of the time, reserving his straight fastball as an occasional change-of-pace pitch against right-handers.)