Jermell Charlo stops Brian Castano in “Fight of the Year” candidate

Jermell Charlo and Brian Castano produced an irrefutable “Fight of the Year” candidate for nine-plus rounds Saturday night.

Then Charlo delivered the knockout he promised in their immediate rematch to become boxing’s undisputed 154-pound champion. Charlo dropped Castano twice during the 10th round and stopped the previously unbeaten WBO junior middleweight champion in a memorable main event Showtime televised from Dignity Health Sports Park.

Referee Jerry Cantu waved an end to what had been incredible action at 2:33 of the 10th round, as Castano struggled to get to his feet a second time.

“I can say it was a little bit nerve-racking,” Charlo told Showtime’s Jim Gray in the ring. “You know, I felt like this was my first fight, you know, when you get nervous and you get ants in your pants. I knew Castano was gonna give it his all. I knew I had trained very, very hard, but you can all see that I came in at [152¾] pounds because I was really in shape and I wanted to make sure that this was my fight.”

Charlo’s career-defining win came nearly 10 months after he boxed to a controversial split draw with Castano in their first title unification fight. Charlo, 31, and Castano, 32, both demanded an immediate rematch after that July 17 bout at AT&T Center in San Antonio.

Charlo was ahead on all three scorecards entering the 10th round Saturday night.