When a runner is on 1st and a batter hits a single to right field the defensive unit swings to the positions diagrammed in Fig. 42. The centerfielder naturally moves to his left to help the right fielder either by backing up, or by calling the play. The left fielder moves in, to back up a possible throw to 2nd. The third baseman covers 3rd with the shortstop some 15 to 20 feet in front of him and in a direct line with the right fielder. The second baseman covers 2nd, the first baseman takes a cut-off position some 15 to 20 feet in front of the catcher but in a direct line with the right fielder. The pitcher, as soon as the ball is hit, runs to a spot at least 15 feet behind 3rd and in a direct line with the third baseman and the right fielder.

Once in position, this is what can happen:

If the hit is fielded cleanly and fast by the right fielder, he should fire at the shortstop’s head. If the lead runner stops at 2nd, the ball is “one base ahead”, as it should be. The shortstop, by the way, should cut the ball off. Baseball Training - Read More.