SAN ANTONIO – Jermell Charlo cannot envision moving up to the middleweight division after boxing Brian Castano on Saturday night.

If Charlo wins their 12-round, 154-pound title unification fight at AT&T Center, he’ll become boxing’s first fully unified champion in that division during the four-belt era. The Houston native wouldn’t have much left to prove, either, in the weight class within which he has competed for almost all of his 13-year pro career.

Charlo, 31, makes the 154-pound limit comfortably, though, and doesn’t see a need to jump up six pounds to the middleweight maximum of 160.

“I make it really easy,” Charlo told a group of reporters after a press conference Thursday at the Thompson San Antonio-Riverwalk hotel. “I’m actually 157 right now. I haven’t even worked out today, so I’m fittin’ to get my workout in. I was walking around 155, 156. So, I’m really a solid 154-pounder. I love it. Like I love this weight division. It’s easy for me to make the weight. I don’t wanna move up to 160 because that contradicts my brother. You know, it contradicts Errol Spence if he wants to move up. Who knows what’s next for me, though?”

Charlo’s twin brother, Jermall, owns the WBC middleweight title and figures to remain a 160-pound fighter for the foreseeable future. Jermall Charlo, who was a 154-pound champion at the same time as his brother, has had difficulty securing high-profile fights since he moved up to middleweight.

That’s another reason Jermell Charlo (34-1, 18 KOs) might want to remain in the 154-pound division after he encounters Castano (17-0-1, 12 KOs). The IBF/WBA/WBC 154-pound champion didn’t mention potential opponents he would like to fight after facing Castano, yet he is confident more challenges exist within the division he has long called home.

“Everybody kinda good,” Charlo said. “You know, like everybody in this division is – you know, I done ran through a bunch of ‘em. But thank God for them. They help pay bills and keep my life living like this. But I’m ready. You know, like everybody in the division that want some of this, they can come get it. I know the young ones coming up and they got some ones that’s wanting to transition over to my division. But that’s why I’ll show y’all Saturday night why it’s kinda like, ‘OK, you gotta second-guess that.’ ”

Charlo-Castano will headline a “Showtime Championship Boxing” tripleheader from the home arena of the NBA’s Spurs.

Las Vegas’ Rolando Romero (13-0, 11 KOs) and Sweden’s Anthony Yogis (24-1-1, 8 KOs) are set to square off in the 12-round co-feature for Romero’s WBA interim lightweight title. Uruguay’s Amilcar Vidal (12-0, 11 KOs) and Immanuwel Aleem (18-2-2, 11 KOs), of Richmond, Virginia, are scheduled to meet in a 10-round middleweight match that’ll open Showtime’s three-bout broadcast at 9 p.m. ET.

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