Jeison Rosario isn’t the least bit content with winning a career-defining fight that completely changed his life.

The IBF/WBA 154-pound champion claims he is even more motivated to beat Jermell Charlo in their upcoming title unification fight than he was when he upset Julian Williams seven months ago. The Dominican Republic’s Rosario is an underdog again, but he is determined to leave the ring September 26 with another impressive victory on his resume and a third world title.

“I’m more hungry than when I acquired the titles,” Rosario said through a translator Tuesday as part of a virtual press conference. “I’m definitely more motivated. The desire inside, the fire is burning inside of me to win this fight against, as we know, a great fighter in Charlo. Like the Dominican people say, we’ve gotta keep moving forward. That’s what I plan to do in this fight.”

Houston’s Charlo (33-1, 17 KOs) is a 4-1 favorite entering his first fight since knocking out Detroit’s Tony Harrison (28-3, 21 KOs) to win back the WBC super welterweight title Harrison took from him almost exactly a year earlier. Charlo knocked out Harrison in the 11th round of their rematch December 21 at Toyota Arena in Ontario, California.

Four weeks later, the 25-year-old Rosario pulled off boxing’s biggest upset of 2020. Williams was a 30-1 favorite, but the undeterred, rugged Rosario overpowered the defending champion and stopped him in the fifth round of a fight FOX televised from Temple University’s Liacouras Center in Philadelphia, Williams’ hometown.

Williams (27-2-1, 16 KOs, 1 NC) declined his contractual right to an immediate rematch in favor of fixing scar tissue above his left eye, which enabled Rosario to face Charlo. Their 12-round fight will headline a Showtime Pay-Per-View event at Mohegan Sun Arena in Uncasville, Connecticut.

Rosario (20-1-1, 14 KOs), who overcame homelessness and other obstacles while growing up in Santo Domingo, wouldn’t say whether he believes Charlo is better than Williams. Nevertheless, he expects a tougher test from the 30-year-old Charlo than Williams provided.

“It’s gonna be a great war,” Rosario said. “I’m dedicated, motivated for this fight. I know what it [takes] to beat a person like Jermell Charlo in this fight. So, the training has also been going great and I’m ready for this fight.” 

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