Ontario, California - In the FOX opener, Mexico's Rene Tellez Giron (14-1, 8 KOs) scored a sixth-round knockout against 2016 U.S. Olympian Karlos Balderas (9-1, 8 KOs) to hand Balderas the first loss of his professional career.

The fight was scheduled for eight rounds, but Giron brought matters to a close at 2:59 of the sixth round when he landed a smashing left hook and caught Balderas on the chin and sent him falling flat on his back to the canvas. Balderas made it to his knees, but couldn't beat the count of referee Ray Corona.

Giron dropped Balderas with a left hook in the third round, but Balderas managed to beat the count and Corona let the fight continue despite the fact that Balderas stumbled backwards when Corona asked him to walk forward.

"After I knocked him down in the third round, I saw his eyes were rolled back like he was hurt, but he has the heart of a lion,'' Giron said.

"He didn't want to lose his undefeated record in front of his people. When he got up, I was like, 'Wow! He got up! He's up!' So, I kept on him and left everything in the ring. I'm really happy. Karlos had said he fought with the best and he was an Olympian. Well, I fought a lot of people too and you see the result.''