FOX’s “American Idol” eliminated a chunk of “The Apprentice” audience Thursday night – siphoning off about 4 million viewers from NBC’s reality show.

Thursday’s special live “Idol” episode, which was delayed an extra day because of Tuesday’s voting snafu, aired head-to-head against “The Apprentice” from 9 to 9:30 p.m.

“Idol” snared 20 million viewers against “The Apprentice,” which averaged 10.8 million viewers from 8:30 to 9:30 p.m. – down from its season average of 14.6 million viewers.

“The Apprentice” usually airs from 9 to 10 p.m., but was moved up 30 minutes so it wouldn’t compete against NCAA basketball on CBS.

When NBC made that move, of course, it didn’t realize Fox would be airing the extra “Idol” show, on which Mikalah Gordon, the 17-year-old singer from Las Vegas, got the boot.

“Idol” returns Tuesday.