CARSON, California – 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.

Houston’s Charlo (35-1-1, 19 KOs) became boxing’s first fully unified 154-pound champion of the sport’s four-belt era. Charlo defended his IBF, WBA and WBC championships and captured the WBO belt from Buenos Aires’ Castano, who lost for the first time in his nine-year professional career (17-1-2, 12 KOs).

Charlo also joined middleweights Bernard Hopkins and Jermain Taylor, junior welterweights Terence Crawford and Josh Taylor, cruiserweight Oleksandr Usyk and super middleweight Canelo Alvarez as one of only seven undisputed champions in any division since boxing began recognizing four sanctioning organizations.

“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, who boxed effectively off his back foot for most of their fight, was ahead on all three scorecards entering the 10th round Saturday night.

Glenn Feldman scored eight of the first nine rounds for Charlo, who was ahead 89-82 on his card. The other two judges – David Sutherland (87-84) and Zachary Young (88-83) – had it closer than Feldman.

CompuBox indicated that their fight was much closer than the judges had it.

CompuBox credited Castano for landing 21 more punches than Charlo (194-of-610 to 173-of-559). According to CompuBox’s unofficial statistics, Castano connected with more power puches (175-of-411 to 142-of-303) and Charlo landed more jabs (31-of-256 to 19-of-199).

Charlo rendered the scorecards unnecessary during the 10th round.

A left-right combination by Charlo punctuated an exchange early in the 10th round. Castano backed Charlo into the ropes and landed a right hand later in the 10th round.

Charlo caught Castano with a left hook that, after a delayed reaction, sent Castano to one knee with 52 seconds remaining in the 10th round. Castano reached his feet by the time referee Jerry Cantu counted to five, but Castano was still reeling.

Once Cantu called for the action to resume, Charlo backed Castano into the ropes, connected with a left uppercut to his head and landed a left to the body that knocked Castano to his gloves and knees with 34 seconds to go in their scheduled 12-round rematch. Castano slowly attempted to get up from that second knockdown, which led to Cantu calling a halt to the action with 17 seconds remaining in the 10th round.

“I listened to my corner this time,” Charlo said. “I got in my bag around the seventh round. I started sitting down a little bit more, instead of boxing so much and moving around. I saw that he was wearing down a little bit and I was breaking him down. I just saw my punches being more effective. I get stronger in the later rounds, if they didn’t know.”

Charlo drilled Castano with a left hook on the inside early in the ninth round. Castano came forward in that round, just as he had done throughout their fight, but he didn’t throw as many punches  in those three minutes as in previous rounds.

Castano and Charlo traded clean right hands just before the ninth round ended.

Charlo connected with a short, left hook in the middle minute of the eighth round. Charlo caught Castano with another flush left hook later in the eighth round, when Charlo boxed well off his back foot yet again.

A right-left combination by Charlo stopped Castano from moving forward briefly early in the seventh round. A left hook by Charlo knocked Castano off balance just before the midway mark of the seventh round.

Charlo clipped Castano with a left hook in an exchange early in the sixth round. A left hook by Castano made Charlo retreat later in the sixth round.

Charlo caught Castano with a left uppercut, but Castano countered with a left hook in the final minute of the sixth round. They closed that round with another hectic exchange in which both boxers landed clean shots.

Charlo moved Castano backward with a right hand early in the fifth round. They then traded punishing power shots during the final minute of an incredible fifth round that brought appreciative fans at this famed venue to their collective feet.

Charlo and Castano landed hard head shots in a violent exchange early in the fourth round. Castano continued to pressure Charlo and they fought at a much faster pace than in their first fight.

Another entertaining exchange highlighted the end of the fourth round, when Castano caught Charlo with two hard right hands. Charlo took those shots well, though, and smiled at Castano after the bell sounded to conclude the fifth round.

Charlo connected with a left up top and then a hard right hand up top several seconds later in the first half of the third round. Castano caught Charlo with a left hook with about 45 seconds to go in the third round, and another left hook about 20 seconds later.

Castano connected with a right to the side of Charlo’s head early in the second round. Charlo missed with several power shots before he landed a left hook with about 1:20 to go in the second round.

Charlo initiated several clinches in the final 30 seconds of the second round. Castano caught Charlo with a left hand that knocked him backward just before the bell sounded to end the second round.

Charlo and Castano traded hard shots after Castano missed with two right hands in the second half of the opening round. Castano connected with a hard right hand, but Charlo came back with a stiff left just before the first round ended.

Their fight started later than anticipated (11:30 p.m. ET), long after Jaron Ennis’ second-round stoppage of Custio Clayton in the co-feature, because Castano arrived at Dignity Health Sports Park long after his scheduled time of arrival. Castano warmed up properly, though, and got off to a strong start against Charlo.

“We both were fighting back and forth,” Castano said. “It was power back and forth, and then his right hand came over and stopped the fight. He’s a champion. He hit me. He got me, but I’m OK.”

Keith Idec is a senior writer/columnist for He can be reached on Twitter @Idecboxing.