A few years back, the video above (highly recommended to wear the appropriate glasses while watching it) was produced by the The New York Times, entitled as “How Mariano Rivera Dominates Hitters”. This 3D iteration accompanied a story on Rivera’s successful signature cutter. This rendering demonstrates the acute similarities between his fastball and cutter that appear to be for the hitter at the plate.
At the time, though, a training tool for hitters that uses realistic graphics and allows them to get hundreds upon thousands of repetitions in a single session didn’t exist. To date, still, there lacks a substantive, software-based answer to aid batters, considering they get limited repetitions at practice, as is, due to time.