Judge Burt Clements has admitted he made a scoring error that cost Manny Pacquiao the WBA and IBF featherweight belts.
Filipino Pacquiao drew with Mexico's Juan Manuel Marquez in Las Vegas on Saturday.
But Clements scored Pacquiao's three knockdown round 10-7 instead of 10-6 and the fight 113-113.
Nevertheless, Pacquiao has been told by the Nevada State Commission he has no grounds for a protest.
"Clearly, it wasn't non-awareness that there were three knockdowns," Clements told the Las Vegas Review Journal.
"I just screwed up. I feel badly because I dropped the ball, plainly and simply."
Judge Guy Jutras mystifyingly scored the fight 115-110 in Pacquiao's favour while John Stewart scored it 115-110 for Marquez.
Many observers thought the champion Marquez had done enough to win it despite his first-round disaster.