LOS ANGELES – Errol Spence Jr. knows Shawn Porter’s persistence is one of the WBC welterweight champion’s greatest attributes.

Spence also is confident that he’ll eventually beat the determination out of Porter in their 12-round, 147-pound title unification fight. The unbeaten IBF champion promised again Friday that he’ll become the first opponent to knock out the durable, gritty Porter on Saturday night at Staples Center.

“I know he’s a tough fighter, he’s gonna come to fight,” Spence told FOX Sports’ Heidi Androl following their weigh-in at the Intercontinental Los Angeles Downtown hotel. “But like I said, I’m gonna break his will and I’m gonna be the first person to stop Shawn Porter.”

The 31-year-old Porter (30-2-1, 17 KOs), of Akron, Ohio, has lost only a pair of 12-round decisions since he turned pro in October 2008.

Kell Brook beat him by majority decision to take the IBF welterweight title from Porter in August 2014 in Carson, California. In June 2016, former WBA welterweight champ Keith Thurman topped Porter by unanimous decision in a closely contested bout. 

The 29-year-old Spence (25-0, 21 KOs), of DeSoto, Texas, anticipates a real challenge from Porter, even though Las Vegas and Internet sports books typically list Spence as a 10-1 favorite.

“He’s a fighter,” Spence said. “He’s a champion, just like me, and we’re gonna get it on. I’ve been wanting the WBC belt for a long time, and now he’s gonna hand it over to me come Saturday night. Or I’m gonna take it off of him.”

Porter has fought Thurman and Brook, and has beaten five former welterweight champions, including Danny Garcia. With all due respect to his long list of quality opponents, Porter feels Spence will provide the toughest test of his career in the main event of a four-fight FOX Sports Pay-Per-View telecast (9 p.m. ET/6 p.m. PT; $74.95 in HD).

“Oh, he knows what it is,” Porter said. “He’s gonna come ready for the fight and I’m gonna come ready for the fight. Listen, y’all are in for a treat. Him and I, best of the best, about to get in the ring and do it. He’s got all the tools, I got all the tools. My tools better than his? His tools better than mine? Y’all about to find out. Great fight.”

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