The boxing world now knows Mario Cazares.

The unbeaten but previously anonymous Mexican upset Julio Cesar Chavez Jr. by technical unanimous decision in their light heavyweight fight Friday night at Grand Hotel Tijuana in Tijuana, Mexico. Cazares (12-0, 5 KOs) defeated Chavez (51-5-1, 33 KOs, 1 NC) on all three scorecards once their scheduled 10-rounder was stopped during the sixth round due to a cut above Chavez’s left eye.

Cazares won by scores of 59-54, 57-56, 57-56. He had a point deducted for an intentional head-butt during the second round.

Before beating Chavez, the 30-year-old Cazares had defeated only one opponent with a winning record. That foe, Eduardo Tercero, was 9-8-1 when Cazares knocked him out in the first round of their scheduled eight-rounder last December 15 in Mexico City.

Chavez, whose hair was dyed blonde, fought with blue and brown tape over his back to cover a tattoo. His legendary father, who sat ringside after defeating Jorge Arce in an exhibition on the undercard, probably wanted to cover his eyes after watching his son lose a second straight bout.

The 34-year-old Chavez fought for the first time since quitting on his stool following the fifth round against Daniel Jacobs on December 20 at Talking Stick Arena in Phoenix.

The scheduled 12-round bout between Jacobs and Chavez had become competitive before Chavez declined to answer the bell for the sixth round. Chavez came in 4¾ pounds overweight for what was supposed to a super middleweight bout with Jacobs (36-3, 30 KOs).

What was developing into an action-packed sixth round Friday night came to an abrupt end when an accidental clash of heads opened a nasty gash over Chavez’s left eye. A ringside physician looked at the cut, decided to stop the bout and they went to the scorecards.

Cazares connected with a left uppercut early in the fifth round. Chavez’s hard jab snapped back Cazares’ head later in the fifth.

An accidental head-butt caused a brief break in the action for Chavez to recover during the middle minute of the fourth round. They traded hard shots in the center of the ring later in the fourth.

Cazares’ right hand rocked Chavez early in the third round. That shot made Chavez retreat.

They traded flush left hooks just before the third round ended.

Chavez landed several right hands during the second round, which left Cazares holding at times. Cazares intentionally head-butted Chavez in the second round, which led to a point deduction.

Chavez clipped Cazares with a right hand just before the second round ended.

Chavez and Cazares tied each other up several times during the first round. Cazares connected with a short right hand toward the end of the opening round, but Chavez took it well.

Earlier Friday night, Julio Cesar Chavez Sr., perhaps the most beloved boxer in Mexico’s rich history in the sport, and Arce engaged in an entertaining exhibition DAZN streamed in the U.S.

The 58-year-old Chavez and the 41-year-old Arce wore headgear and T-shirts for their four-round exhibition.

They traded hard body and head shots throughout what amounted to a spirited sparring session. Chavez and Arce each had his moments in the bout, but Chavez was declared the winner.

They had to be separated after the bell rang to end the third and fourth rounds. Arce and Chavez landed punches after each of those two rounds concluded.

Despite those fouls, Chavez and Arce showed sportsmanship and respect toward one another after Chavez had his hand raised.

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