Major League Baseball and the players' union have banned rolling block slides to break up potential double plays.

The rule change was made in hopes of preventing a repeat of the takeout by Chase Utley that broke a leg of Ruben Tejada in the postseason last fall.

Under the rules change, a runner must make a "bona fide slide," defined as making contact with the ground ahead of the base, being in position to reach the base with a hand or foot and to remain on it, and sliding within reach of the base without changing his path to initiate contact with a fielder.

An umpire can call both the runner and batter out for a violation.