From the New York Times In Class AAA, the size of first, second and third base will increase to 18 inches square, from 15. In Class AA, at least four defensive players must be positioned on the infield, each with both feet completely in front of the outer boundary of the infield dirt. In the second half, M.L.B. may require two infielders to be positioned entirely on each side of second base. In high-Class A, pitchers must step off the rubber before attempting a pickoff throw, and in both low-Class A leagues, pitchers will be limited to two step-offs, with a third resulting in an out or a balk. In the low-Class A Southeast League, umpires will use an automated ball-strike system (A.B.S.) to call pitches. In the low-Class A Southwest League, on-field timers will enforce the time between pitches, innings and during pitching changes.