SAN ANTONIO – Mario Barrios started slower than he would’ve liked Saturday night, but Barrios eventually delivered the knockout of Ryan Karl that he expected.

Barrios knocked out Karl in the sixth round of their scheduled 12-round, 140-pound title fight on the Gervonta Davis-Leo Santa Cruz undercard at Alamodome, where his hometown fans cheered wildly. Referee Luis Pabon stopped their bout at 2:23 of the sixth round, once Barrios’ left hand sent a bloodied and battered Karl to the canvas.

Barrios blasted Karl with a short, left uppercut before finishing him off with the aforementioned left hand to the side of his head. Karl fell to his side and rolled over, flat on his back, before Pabon stopped the action.

The 25-year-old Barrios became the first boxer from San Antonio to successfully defend a world title. Barrios (26-0, 17 KOs), who was a 25-1 favorite, retained the WBA world super lightweight championship he won by beating Batyr Akhmedov in controversial fashion in his previous fight, a 12-rounder 13 months ago at Staples Center in Los Angeles.

The 28-year-old Karl (18-3, 12 KOs), of Milano, Texas, lost by knockout for the third time in his career. He had won three straight bouts before Barrios beat him.

Barrios caught Karl with a right hand 20 seconds into the sixth round that made Karl use his gloves to keep from falling to the canvas. That counted as a knockdown, but Karl courageously tried to fight out of that trouble.

A clash of heads later in the sixth opened a gruesome gash above Karl’s right eye. Pabon called for a break for a ringside physician to look at Karl’s cut, and Barrios dominated the action thereafter.

Barrios battered Karl’s body during the fifth round. Karl kept coming forward, but he couldn’t land the type of clean shots on Barrios he did during the second and third rounds.

Barrios hurt Karl with a right hand early in the fourth round, which made Karl stumble backward. A straight right hand by Barrios also caught Karl clean just before the fourth round ended.

Karl drilled Barrios with a straight right early in the third round. A right-left combination by Karl connected about 1:10 into the third round, when he surprisingly continued to make Barrios uncomfortable.

Karl appeared to affect Barrios with a right hand in the opening minute of the second round. A short right hand by Karl connected with about 1:15 remaining in that second round.

Barrios landed two lefts back-to-back with just over 20 seconds remaining in the first round. Karl appeared to hit Barrios behind the head multiple times in the opening round, but he wasn’t warned by Pabon. 

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