8.05 (d): If there is a runner, or runners, it is a balk when ... [t]he pitcher, while touching his plate, throws, or feints a throw to an unoccupied base, except for the purpose of making a play; I understand "unoccupied base" in that context to mean a base not currently occupied by a runner. Not a base not covered by a fielder. Else, any time you throw to second, you are throwing to an unoccupied base, because those plays are generally one where the fielder sweeps in while the ball is coming. That is how I understood it too. Otherwise Bobby Valentine's Dancing Olerud Strategy would have been a balk every time, no?