If an announcer describing each pitch during a baseball game fails to notice a naked fan running across the infield, the announcer would be demonstrating:

an inattentional blindness

Explanation:

It would be rational to think that since the eyes of the announcer at the baseball game were open, the individual would be able to see things happening close by. The obvious reason why he or she failed to notice the naked fan running across the infield was inattentional blindness.  

This happens when an individual (just like the announcer) fails to notice a fully-visible object that appears unexpectedly because the person’s attention was wholly fixed on another event.