By Keith Idec (photo by Ryan Hafey)

LAS VEGAS – It took about half an hour, but the Errol Spence Jr.-Shawn Porter press conference finally got a little heated Saturday afternoon.

Porter took exception to Spence stating that he took the wrong approach to his last fight – an unimpressive, split-decision defeat of Yordenis Ugas on March 9. Once they began exchanging words, Spence predicted what he had refrained from saying earlier in the media center for the Manny Pacquiao-Keith Thurman fight at MGM Grand.

“I’m knocking his ass out,” Spence said. “This is the same dude that had a tough fight with [Adrian] Granados. So, I’m not trying to hear none of y’all talk. Every time he stepped up, he lost. The only person he stepped up and beat was Danny Garcia. He fought Keith Thurman. Kell Brook came over here and took the [IBF] belt from him, and hurt him a couple times.”

When Porter pressed Spence for a prediction, Spence disrespectfully responded, “I’m gonna beat you up. You know I’m gonna punish you!”

Spence (25-0, 21 KOs), the IBF welterweight champion, and Porter (30-2-1, 17 KOs), who owns the WBC 147-pound crown, will meet September 28 in a FOX Sports Pay-Per-View main event at Staples Center in Los Angeles.

Porter, 31, is the type of accomplished opponent Spence, 29, has tried to get in the ring throughout his ascent in the welterweight division. He dominated four-division champion Mikey Garcia in his last bout, but Garcia (39-1, 30 KOs) moved up from lightweight to welterweight to challenge Spence on March 16 at AT&T Stadium in Arlington, Texas.

A week earlier, Porter escaped with a narrow with against Ugas (23-4, 11 KOs) at Dignity Health Sports Park in Carson, California.

“Ugas is a good fighter,” Spence said. “Ugas is good, tough. He was a Cuban Olympian, a guy who always comes to fight. I think Shawn had the wrong game plan. Shawn tried to box him and tried to out-point him, and that’s just not him.”

Porter disputed Spence’s assessment and questioned Spence’s boxing ability.

“You try to box me, and you see what happens,” Spence said. “You try to box me and see what happens. I’ll put you on your ass! You try to box, see what happens.”

When Porter persisted, Spence kept at it, too.

“Yeah, you did have the wrong game plan,” Spence said. “A lot of people thought you lost.”

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