Boxing: Julian Williams is confident in facing Jeison Rosario on Saturday at the Liacouras Center

Dressed in an all-black ensemble, one punctuated by his purple hair, a gold chain and sunglasses, Chris Colbert delivered Muhammad Ali-like boasts when it was his turn to speak during a prefight news conference Thursday at the Liacouras Center.

Colbert will fight on the undercard of the Julian “J-Rock” Williams-Jeison Rosario super-welterweight championship bout Saturday night at Temple’s arena. On Thursday, he sat alongside Williams, who despite being the champion and the nationally televised card’ centerpiece, looked more like a guy waiting for the subway.

While most of the other fighters on stage betrayed their excitement with bold predictions, the West Philadelphian, wearing white sneakers, a drab, loose-fitting sweatsuit, and a baseball cap, slumped casually in his chair.

“I’ve been a professional almost 10 years,” Williams said afterward. “I’ve had almost 30 pro fights. I’m relaxed. I’m taking it easy. I’m just looking at the clock.”

Two days out from his first defense of the unified championship he took from Jarrett Hurd in a spectacular bout nine months ago, Williams was nearly finished with his grueling training regimen. The last and in some ways the most challenging item on his prefight checklist will be enduring those long hours Saturday before he steps into the ring late that night to face the rangy Dominican challenger.

“I’m going to try to be just normal on Saturday, like it’s just a day off from the gym,” Williams said. “I’ll just do some things to pass time. Lay around. Eat lunch. Do some stretching. Watch some TV. Do a little bit of reading.”

Though he did it with a deadpan, “been-there, done-that” demeanor, the 29-year-old champ who coincidentally has had 29 fights (27-1-1, with 16 KOs), didn’t seem to think the younger Rosario had much of a chance.

“He said he thinks it’s going to be a war,” said Williams. “That’s the only thing he can do to have a chance. But I’m going to step on him. … He can’t outbox me. He can’t out-skill me. He’s sure not going to out-will me.”

Interestingly, before his May fight with Hurd, Williams had considered hiring Rosario, who’s been living and training in South Florida, as a sparring partner. He eventually decided he didn’t want to work out with a fighter he might have to face down the road.

“There were plenty of guys in Philly to choose from,” he said.

Rosario, nicknamed “Banana” because like Popeye and spinach he believes he derives his power from the fruit, doesn’t figure to be a pushover. He has lost just once in 21 fights and has won his last eight in succession.

“I’m not worried about fighting in his backyard,” Rosario said through an interpreter. “I’ve never fought in my own country so I’m used to it.”

For Williams, who briefly lived in a Roosevelt Boulevard homeless shelter as a youngster, Saturday night’s will be just his third Philadelphia fight and his first since 2011, a year after he turned pro.

“I’m blessed to be making my first title defense here in Philadelphia,” Williams said, “but to be honest I’m so locked into this fight that I haven’t even thought about it. I don’t want to get caught up in the hype and cameras.”

On Friday, just about the only thing that animated Williams was when Rosario’s trainer, Luis Perez, suggested that his fighter was relaxed because he had “nothing to lose.”

“Nothing to lose?” Williams flared. “His coach ain’t taking no punches. But he [Rosario] could lose his life. We lost four fighters in the ring last year.”

Williams’ trainer, Stephen Edwards, said his fighter had prepared tirelessly, an indication that he’s as hungry now as he was as a 20-year-old.

“I wanted to be champion of the world,” Williams said. “I set goals for myself and now that I’ve done that, I set a new goal … to be pound for pound the best in the world. Why not?”

In Saturday’s other Liacouras Center fights, the unbeaten lightweight Colbert (13-0), a Brooklynite nicknamed “Prime Time,” will take on Jezreel Corrales in what’s being billed as a co-main event, and Reading’s Erik Spring will meet top super-welterweight prospect Joey Spencer.