Yes, it's just one pitch that he has to control, but his precision of his cutter is unmatched by any pitch from any pitcher in the majors.
B.J. Upton and Carl Crawford were both caught looking, and both disagreed with the call. Unfortunately for them, the overhead view of both pitches showed that Rivera's pitches were strikes, and he truly can place the ball anywhere he wants. Not only can he put his pitches anywhere in the zone, but he has a perfect understanding of where the hitters' hot and cold spots are. He even made Evan Longoria swing and miss twice, and only wasted one pitch in the at bat (probably intenionally) before striking him out.
I hope his control will be noted when his career is finally said and done.