Unheralded Josesito Lopez stopped welterweight Victor Ortiz on Saturday night in Los Angeles, apparently breaking Ortiz's jaw in the ninth round to earn a stunning upset victory.

Ortiz and his corner stopped the fight before the 10th-round bell when the injury left Ortiz unable to close his mouth.

Oritz was reportedly ahead on all scorecards in the Staples Centre bout, 88-83, 87-84 and 86-85.

Lopez (30-4, 18 KOs) leaped onto the ropes to celebrate one of the biggest upsets in recent boxing history. Lopez accepted the fight last month as a late replacement for Andre Berto, who failed a doping test that scuttled his rematch with Ortiz.

"I knew I had to fight the fight of my life to win," said Lopez, a Riverside native who has never fought for a world title. "I knew the longer it went, the better chance I'd have. He hits hard, but I was never going to quit. I knew it was a close fight on the scorecards, and I knew I could press him more and more if I continued. He's like a tree. I had to chop him down."

Ortiz (29-4-2) last fought in September 2011, when he was stopped by Floyd Mayweather. Ortiz intentionally headbutted Mayweather and then apologized and kissed Mayweather after the infraction. When the referee waved the fighters back to action, Ortiz had his hands down and was knocked out by a Mayweather right.

Unbeaten Saul Alvarez, who was in attendance, was also left smarting from the result. If Ortiz emerged unscathed, he was scheduled to fight Alvarez in a pay-per-view junior middleweight bout on Sept. 15.

Alvarez has seen two other opponents for that bout fall through. Paul Williams was injured in a motorcycle crash that could leave him paralyzed for the rest of his life, while James Kirkland subsequently pulled out.

Although Ortiz repeatedly tagged Lopez with shots throughout the bout, producing swelling around both of Lopez's eyes, Lopez repeatedly replied with big shots of his own -- and he even taunted Ortiz with come-at-me gestures, thrilling the crowd.

"I'm a man, and I'm not intimidated by anything," Lopez said. "I have a big heart. He tried to intimidate me, but it didn't work. Victor has no heart."

Ortiz showcased his superior skill and power from the opening round, repeatedly putting Lopez on the retreat. Yet Lopez constantly found ways to respond, either through counterpunching or his own strong shots to Ortiz, who has never been a defensive technician.

Lopez used his longer reach to pick at Ortiz, who occasionally showed frustration in a clinch. Ortiz also hit Lopez with a rabbit punch in the back of the head, earning a caution from the referee and the jeers of fans.

On Saturday's undercard, Argentina's Lucas Matthysse proved too strong for Humberto Soto in a junior welterweight bout. Soto, moving up in weight, did well enough in the first two rounds, but was gradually worn down by the bigger man.

Matthysse decked Soto just before the bell to end the fifth, and the Mexican fighter's corner signalled to the referee before the sixth that they're fighter could not continue.

With files from CBCSports.ca