On a single to right field the shortstop will be the cutoff to third base. The second baseman will cover second base. The pitcher must hustle to get in position to back up third base. The left fielder should move in to help back up third base.
With younger players you may want to have the second baseman be the cut on this play. It depends on the arm strength of the right fielder. In general you want to have the second baseman be the cutoff person if the shortstop would have to go on the second base side to be in proper position.