Mayer (15-0, 5 KOs), ranked No. 5 on the ESPN.com pound-for-pound list, rocketed to stardom following her appearance at the 2016 Rio Olympics. Less than two years after her August 2017 professional debut, she shined on the Tyson Fury-Tom Schwarz undercard. In July 2020, Mayer blanked Helen Joseph by unanimous decision in the first female main event since the newest incarnation of Top Rank on ESPN boxing premiered in July 2017. On Halloween evening 2020, she dominated longtime champion Ewa Brodnicka to earn the WBO title. She made her first title defense in June at Virgin Hotels Las Vegas and turned back two-weight world champion Erica Farias over 10 rounds.