The Automatic Balls and Strikes system, commonly referred to as ABS, will be deployed in two different ways. Half of the Class AAA games will be played with all of the calls determined by an electronic strike zone, and the other half will be played with an ABS challenge system similar to that used in professional tennis.
Each team will be allowed three challenges per game, with teams retaining challenges in cases when they are proved correct. MLB's intention is to use the data and feedback from both systems, over the full slate of games, to inform future choices.
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