Jermell Charlo became the unified junior middleweight champion with a 10th-round knockout victory over Brian Castano in their highly-anticipated rematch at Dignity Health Sports Park on Saturday.

Charlo is the seventh undisputed champion of boxing's four-belt era and the first to unify the 154-pound division since Winky Wright in 2004.

Charlo led on all three scorecards when he knocked out Castano, according to ESPN's Mike Coppinger.

The fight was delayed due to Castano arriving late to the venue. Once the bell sounded, Saturday's rematch became another instant classic. Both fighters warred from the opening bell, and several early rounds ended with frantic exchanges of punches.

Ultimately, Charlo pulled away by using his power. The fighters were relatively even in total punches landed - Charlo landed 31% to Castano's 32% - but "Iron Man" had a bigger edge in power punches, landing 47%, per CompuBox.