Fastball command is a good thing for a pitcher to have. In 2016, pitchers across the league threw their four-seam fastballs 36.4% of the time, according to Pitch F/X. They also threw their four-seamers, two-seamers or sinkers 56.6% of the time. Naturally, if a pitcher plans on throwing a certain category of pitches over half of the time, it is important that his ability to locate is up to par.
The problem is that quantifying command is extremely difficult. Nonetheless, Jeff Long, Jonathan Judge, and Harry Pavlidis recently gave it a try for Baseball Prospectus. They use a statistic called CSAA (Called Strikes Above Average) to quantify a pitcher’s command, calling upon a stat that is often used to quantify a catcher’s pitch framing ability.