There's about a million reasons why measuring defense is difficult, but among the most important is this simple question: Which plays are the most important to measure? That's not an issue on offense, where every plate appearance offers the hitter a chance to do something notable. But on defense, it's important to separate the lazy pop fly that's an out 99 percent of the time from the low liner that's caught only 20 percent of the time.
So that's exactly what we've done. Using Statcast™ exit velocity and launch angle -- it's important to use both, because even a 120 mph rocket that is hit straight up will still be an out -- we've identified a range of line drives and hard-hit flies that are a hitter's best friend, the kind of ball that has a .