The main card for UFC 251 Live Online is headlined by welterweight champion Kamaru Usman’s title defence against Gilbert Burns. Born in Nigeria, Usman has never been defeated in 11 UFC appearances, with a professional mixed martial arts record of 17-1. He captured the welterweight crown in March last year when he defeated Tyron Woodley by unanimous decision. Usman last fought in December, defending his title against Colby Covington.Burns, meanwhile, moved into the No 1-ranked challenger spot following his resounding victory against Woodley on May 30, when he dominated the former champion in five rounds to take a unanimous decision. The Brazilian, whose record stands at 19-3, fought also in March and currently rides a six-fight win streak. Elsewhere, featherweight champion Alexander Volkanovski and Max Holloway will go head-to-head for the second time in a rematch of their December clash. Australian Volkanovski won the original bout by unanimous decision to take Holloway’s title. Rounding out the title fights, Petr Yan and Jose Aldo will face off for the vacant bantamweight crown following champion Henry Cejudo’s decision to retire last month.