Mike Petriello at mlb.com has a story about the new fielding metric called "Outs Above Average" or OAA. He links to a much more detailed background piece by Tom Tango on the MLB Tech blog. Both are long but are worth a look--there is a whole new world out there because of Statcast and we have to start learning about it. I should note that the articles are particular to the infield component of OAA, the outfield stuff is handled differently.
Since all batted balls are tracked (via radar) and the movements of all the players tracked as well (via stereo camera systems) the combination of the two technologies allows for the measurement of speed, direction, distance, and more on every play.