LOS ANGELES – Jermell Charlo regrets not finishing Brian Castano when he felt he had the opportunity to stop him during the 10th round of their 154-pound title fight last July 17.

Had Houston’s Charlo closed out that fight in the manner he prefers, they never would’ve gone to the scorecards, which forced the IBF/WBA/WBC champion to settle for a 12-round split draw at AT&T Center in San Antonio. Judge Nelson Vazquez curiously scored Charlo a 117-111 winner of a fight that was closer, but Steve Weisfeld scored Castano a 114-113 winner and Tim Cheatham had it even, 114-114.

Charlo was especially effective in a one-sided 10th round, which Weisfeld scored 10-8 for him, a rarity without the benefit of a knockdown.

His left hook wobbled Castano with 1:40 to go in that round. Charlo’s right hand then affected Castano with just over a minute remaining in the 10th round. Another right hand by Charlo moved Castano backward a few seconds before the 10th round ended.

Charlo lamented during a press conference Thursday at The Westin Los Angeles Airport to promote their immediate rematch that he didn’t stop Castano in that 10th round.

“I didn’t finish him, so, you know, that’s the only mistake that I made, is not finishing him,” Charlo said. “I’m usually a closer and so we’re gonna go into this fight with that already on the back of our mind. Once he get like that again, and hopefully it’s earlier than later, um, it’s over.”

The 31-year-old Charlo had won each of his three previous title defenses by knockout – against Jorge Cota, Tony Harrison and Jeison Rosario. He knocked out Mexico’s Cota in the third round, Detroit’s Harrison in the 11th round of their rematch to regain his WBC belt and the Dominican Republic’s Rosario in the eighth round to win the IBF and WBA championships.

“That’s what the f--- I do!,” Charlo said. “I’m knocking him [out]! That’s what I do! That’s what I’m known for. I’m known for the power. I’m known for the knockout. I’m known for the speed. He know it. He know it. But ask him.”

Castano contended later that he didn’t think Charlo’s power was unlike anything he has previously felt in the ring. Regardless, Charlo has been installed as more than a 2-1 favorite by Caesars Sportsbook to win their second fight at Dignity Health Sports Park in Carson, California.

The 12-round bout between Charlo (34-1-1, 18 KOs) and Castano (17-0-2, 12 KOs) will headline a “Showtime Championship Boxing” tripleheader scheduled to begin at 9 p.m. ET and 6 p.m. PT.

Barring another draw or a no-contest, the Castano-Charlo winner will become boxing’s first fully unified 154-pound champion of the four-belt era.

There have been only six undisputed champions during that time in any division. They include middleweights Bernard Hopkins and Jermain Taylor, junior welterweights Terence Crawford and Josh Taylor, cruiserweight Oleksandr Usyk and super middleweight Canelo Alvarez.

The co-feature of Showtime’s telecast will match Jaron Ennis (28-0, 26 KOs, 1 NC), an elite welterweight from Philadelphia, against Custio Clayton (19-0-1, 12 KOs), of Ottawa, Ontario, Canada. This three-bout broadcast will open with a 10-round battle between Mexican junior featherweight contender Kevin Gonzalez (24-0-1, 13 KOs) and Puerto Rico’s Emanuel Rivera (19-2, 12 KOs).

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