This can be an effective play at getting the lead runner, and doesn't require a catcher with a strong arm.
As the pitch is thrown and the runner from first steals, the second baseman will cover second base. The shortstop will come straight in toward the grass. Instead of firing the ball to second, the catcher will throw the ball to the shortstop. The runner at third will not be able to tell that the ball is not going to second until the play is already developed. In fact if he has been taught to break when the ball clears the pitchers head, he many not know the shortstop caught the ball until he is in the dugout.
Most coaches will run the shortstop in front of second. This is a longer run and the shortstop cannot see the runner. In addition, by throwing the ball on the third base side of second base, the shortstop is in a position to catch and throw to third if the runner has decided not to go, but is too far off third.
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