SAN FRANCISCO – Karim Mayfield strutted around the Fillmore District with an air of confidence. It was the same coolness he carried when he roamed the streets as a youngster in the Bay Area neighborhood preparing for a fight. Mayfield was known on the streets as “The Hard Hitta”, a brawler who everyone knew “had hands” and would defend his turf. He didn’t seek fights out, but never backed down from a challenge.

On this Tuesday night though, Mayfield was days away from a different kind of fight, one that if he prevails, will give him an established identity in a craft he took up at the advanced age of 20. With his HBO debut against action brawler Mauricio Herrera on Saturday at the Turning Stone in Verona, N.Y. (10 p.m. ET), he plans to show the whole world he “has hands.”

“You gotta’ show you have hands,” Mayfield told RingTV.com. “There ain’t no running to your family members, you gotta prove yourself. And you gotta look good doing it. I need a good showing overall. You can’t just win nowadays, if you want to be on TV you either have to be in a war, you have to be overly dominant or you have to knock somebody out. I look forward to dominating and getting him out of there.”

Mayfield (16-0-1, 10 knockouts) turned pro at the advanced age of 25. It’s rare for a fighter to start so late and have success, but Mayfield knew he had a future in boxing when he was a wide-eyed amateur in camp with undisputed welterweight champion Zab Judah in 2006, helping Judah prepare for Carlos Baldomir, a bout he lost in the 2006 in THE RING’s Upset of the Year.

“I not only held my own, I was the best sparring partner in the camp,” said Mayfield. “That was the big moment for me. Going into camp I had read in Ring magazinethat he had broken one of his sparring partners’ jaws and broke another one’s ribs. So going in there it was a little mind-boggling. After a few rounds I’m like ‘Woah, what’s going on, maybe he’s just having a bad day,’ but being in camp the whole time I saw it wasn’t him having bad days, it was me having good days.”

The 31-year-old Mayfield turned pro six months later and hasn’t lost since. He made a statement on ESPN 2’s Friday Night Fights with a knockout of Ray Serrano in May, which catapulted him to the HBO date with Herrera, who is coming off a decision loss to Mike Alvarado in April in a brawl.

“He’s definitely a game opponent, he comes to win, he comes to fight,” said Mayfield. “I think it’s a good matchup. I don’t look at it as a tune-up, I don’t look like I’m in over my head at all. He’s definitely going to be a good test for me.”

Mayfield believes his street fighting past helps him in the squared-circle, giving him the tough mentality needed to brawl it out when necessary. It’s something he learned during a rough upbringing in San Francisco.

“People think ‘oh, it’s San Francisco, but in every city there’s a grimy part and a grimy neighborhood,” said Mayfield. “I probably have about 40 obituaries of friends who died. There was a lot of drug dealing going on, a lot of shootings and murders and things like that. There were definitely projects around and you had to hold your own. You had to make a name for yourself in the streets, to be known as a fighter. I wasn’t a tough, mean guy or anything like that. But they would say “Karim’s got hands”. I was known for having hands.

“There’s no weight class in the streets. If you talk the talk, you have to be able to walk the walk. Anytime anyone would want to get into it with my cousins, I would be like [I’ll fight you]. I just wanted to fight. I wanted to be the one that fights their battles. I would have a lot of street fights. I was a cool guy but [people on the streets] knew I liked to fight.”

Though Mayfield has a brawling background, he has recently linked up with 2011 BWAA Trainer of the Year Virgil Hunter, best known for molding Andre Ward into one of the best fighters on the planet.

“He’s helped me to be able to use my skills and do certain things that I may not have known what to do [in the past],” said Mayfield. “Overall he’s helped me to work on my strengths and to also fix some of my weakness, like not using my left hand and not using my jab. He hasn’t tried to make me a full-fledged technical fighter, he’s still letting me be me.

The fight with Herrera was originally slated to take place in Aug. on ESPN 2’s Friday Night Fights, but Herrera pulled out with a back injury. It turned out to be a blessing in disguise for both fighters.

“It’s a bigger stage, bigger pay, and it’s the same opponent,” said Mayfield. “I welcomed it with all open arms. I had a good opportunity to be able to train for this date. A lot of times I’ve had two weeks’ notice but this time I had a full camp.

With a victory Saturday, Mayfield can make his case for being one of the new names to watch in the sport.”

“It keeps me on HBO. It gives me a chance to fight one of those top 140 guys. Any one of those guys with a belt, it’s a natural for me to call out one of those guys [following a win].”