LONDON -- Daniel Dubois left Anthony Joshua's career in disarray after knocking out his English rival with a right to the jaw in Round 5 in a first defense of his IBF world heavyweight title Saturday.

Joshua (28-4, 25 KOs) endured a nightmare as Dubois (22-2, 21 KOs) floored him four times in Rounds 1, 3 and 4 before the savage finish after 59 seconds of Round 5.

Despite being the champion, Dubois pulled off an upset to inflict a fourth professional defeat on Joshua who was denied becoming a three-time world heavyweight champion in front of 96,000 fans at Wembley Stadium, the biggest postwar crowd for a boxing event in the United Kingdom.

Much was made of Joshua's knockout form, and he entered the fight on the back of a vicious stoppage of Francis Ngannou in March. But it was Dubois' power and aggression that determined the outcome as he dominated Joshua, who was on jelly legs from the first round.

Victory sets up the possibility of Dubois fighting for the undisputed world heavyweight title in 2025, against the winner of the Dec. 21 clash between WBC, WBA and WBO champion Oleksandr Usyk and Tyson Fury, who were both ringside.

Usyk stopped Dubois in Round 9 in August last year. Joshua must now hope for a Dubois rematch, or perhaps a clash versus the loser on Dec. 21 after another serious setback to his career.