Regis Prograis almost didn’t make it through the first couple weeks of his inaugural training camp in Las Vegas.

Prograis missed his three kids, who were home with their mom in Rosenberg, Texas. The former WBA/WBC 140-pound champion contemplated, too, whether this was the appropriate time for him to start pushing himself harder than ever alongside so many younger, hardworking fighters.

Ultimately, Prograis realized that was precisely why he changed trainers, from longtime chief second Bobby Benton to Kay Karoma, and shifted sites from Houston to Las Vegas.

Sparring the same fighters repeatedly stunted Prograis’ growth and motivated him to completely change the way he prepared for his first fight since British southpaw Jack Catterall beat him by unanimous decision Oct. 24 at Co-op Live Arena in Manchester, England.

Prograis (29-3, 24 KOs), a New Orleans native, is scheduled to face former IBF junior lightweight champ Joseph Diaz Jr. (34-7-1, 15 KOs) in a 10-round co-feature Saturday night in Chicago. Prograis, 36, and Diaz, 32, will box before DAZN streams a 12-round main event between Kenneth Sims Jr. (22-2-1, 8 KOs) and Oscar Duarte (29-2-1, 23 KOs) from the University of Illinois-Chicago’s Credit Union 1 Arena (8 p.m. ET; 1 a.m. BST).

“This camp has been the hardest camp of my life mentally, physically and emotionally, just because I never did this before,” Prograis told The Ring. “I came to Vegas to train. These guys out here work so hard. I don’t know if it’s because I’m getting older, but I never did this type of work before in my life.

“I came out here just to give myself a chance. My thing is I wanna be a three-time champion and felt like I had to make some changes in my camp. For me, Vegas was a good place because it’s no distractions [there]. … It’s real good work out [there]. That’s why I made the move to Vegas at this stage of my career.”

Prograis recognizes skeptics see him as a different fighter than he was before he lost his last two fights — a pair of 12-round unanimous-decision defeats to Catterall (31-2, 13 KOs) and former undisputed lightweight champ Devin Haney (32-0, 15 KOs, 1 NC). The gritty Prograis was knocked down once by Haney and twice by Catterall, yet the strong southpaw still feels like he can become a three-time champion in the junior welterweight division.

“I accomplished everything I wanted to do in boxing,” Prograis said. “I became a champion, then a two-time champion. I made some good money and invested well, but it's about more than that right now. I wanna chase history and know I have so much more left in the tank. I’m doing so much better and just learning more now.”

Karoma urged Prograis to box more and brawl less in sparring sessions the past two months in Las Vegas. Prograis took less punishment by adhering to Karoma’s teachings and is committed to applying what he learned in camp versus Diaz.

Prograis is a 10-1 favorite, according to DraftKings, to defeat Diaz, a southpaw from South El Monte, California. Diaz is 2-6 in his past eight bouts.

“I think it’s a good fight for me all around,” Prograis said. “It’s a good comeback fight. I’m not overlooking him or nothing like that. But at the same time, the work I did [in Las Vegas] was work I never did in my life. It was work on the skills side, also. I feel like I’ve been getting better. I really wanna show my skill and show that I’m not the same fighter that I was.”