Tim Tszyu was ringside as American Jermell Charlo became the first undisputed super welterweight boxing champion in the four-belt era by stopping Argentina's Brian Castano in a brutal rematch in California.
After an outstanding bout with ample toe-to-toe action, Charlo (35-1-1, 19 KOs) dropped Castano twice in rapid succession in the 10th round in Carson on Saturday night.
Charlo leaped onto the ropes in celebration while the referee was still counting out his opponent, celebrating the addition of Castano's WBO 154-pound title to his WBC, WBA and IBF belts.
Undefeated Australian Tszyu flew in to observe the fight as the WBO's mandatory challenger.
Charlo survived several impressive early rounds by Castano (17-1-2) in the rematch of the fighters' split draw 10 months ago in Texas.
He became only the seventh fighter to simultaneously hold every major title in any weight class since the four-belt era began in 1988.
Charlo, the twin brother of middleweight champion Jermall Charlo, executed a tactical, counterpunching game plan impressively at Dignity Health Sports Park, the famed outdoor stadium south of downtown Los Angeles.
Castano's aggression and Charlo's sharp counterpunching led to big exchanges in every round, highlighted by a sensational fifth round of relentless action. Castano's relentless early pace slowed in the middle rounds, and Charlo ended it in dramatic fashion at 2:33 of the 10th.
After catching Castano with a right uppercut and a left hook for the first knockdown, Charlo dropped Castano again seconds later with two left hands to the head and a left to the body.
Charlo's victory is a landmark moment in the history of top fighters between middleweight and welterweight.
The 154-pound division was created in 1962, and talents ranging from Thomas Hearns and Terry Norris to Felix Trinidad and Winky Wright have excelled at the weight. But no boxer had held every major title at super welterweight since the WBO formed and inaugurated the four-belt championship era in 1988.
Australian Associated Press
Sign up for our newsletter to stay up to date.