General view of the ring prior to the 2012 U.S. Men's Boxing Olympic Team Trials at the Mobile Civic Center. (Kevin C. Cox / Getty Images photo)
Simpson, 17, of Chicago Vocational High School, beat Emilio Sanchez 21-15 Thursday night in Mobile, Ala.
That gives Simpson another shot at Rau'shee Warren, 24, of Cincinnati in the 114-pound class.
Warren, a two-time Olympian and 2007 world champion, won the champions bracket Wednesday by beating Simpson 34-20 in what has been called the most exciting fight of the tournament.
Simpson must now beat Warren twice to win the Olympic trials, a double-elimination tournament.
Warren had first-round losses in the 2004 and 2008 Olympics. He was the first U.S. boxer since 1992 to compete in a second Summer Games.