Mayweather-Cotto undercard results

Carlos Quintana (left) delivered a notable upset Saturday with his sixth-round knockout of DeAndre Latimore on the Mayweather-Cotto undercard. (AP)

Check back on SI.com later for a full-length column on tonight's co-feature bout between Canelo Alvarez and Shane Mosley.

LAS VEGAS -- Up-and-coming welterweight Jessie Vargas, a much fancied Floyd Mayweather protege, stayed unbeaten (19-0, 9 KOs) with a unanimous-decision victory over late replacement Steve Forbes (35-11, 11 KOs).

"It feels great," said Vargas, who won by scores of 100-90, 97-93 and 98-92 on the three judges' scorecards. "I showed my boxing skills. I was in there with a veteran and I outboxed him. It was a totally different game plan with just a week to prepare, [but] I showed I can box any style."

Said Forbes: "He moved around more than I thought. It was smart on his side. I'm not really a welterweight and I took this fight at the last minute; I thought it was a closer fight than [the scores]."

Carlos Quintana, a former welterweight titleholder considered well past his prime, surprised the half-full MGM Grand Garden Arena with a vicious sixth-round knockout of DeAndre Latimore. The 35-year-old Quintana (29-3, 23 KOs) punctuated a string of punches with a lunging left that floored Latimore (23-4, 17 KOs), a well-regarded Mayweather Promotions prospect, who nearly rolled out of the ring before rising to his feet. Yet referee Kenny Bayless was unsatisfied with Latimore's response, calling a stop to the halt to the action at 2:19 of the sixth.

"It was a very good fight, I'm very happy," Quinatana said afterward, who predicted a "very good night for Puerto Rico."

"I kept going for his eye and it paid off," said Quintana, who connected on 108 of 328 punches (33 percent), compared to 55 of 237 (23 percent) for Latimore. "I went 15 months without fighting, so it's great to be back."

Miguel Cotto and his wife observed the Quintana upset from ringside before retreating to the locker room afterward to prepare for the main event.

In the last fight of the non-PPV undercard, Puerto Rican featherweight prospect Braulio Santos (6-0, 5 KOs) scored a unanimous-decision victory over Juan Sandoval (5-9-1, 3 KOs) of San Bernardino, Calif. Extended the distance for the first time in his career, Santos roughed his way to a wide but hard-fought verdict, winning 59-55 on all three judges' scorecards.

Omar Figueroa (16-0-1, 13 KOs) scored a second-round TKO of Robbie Cannon (12-7-2, 6 KOs) in an eight-round lightweight fight. Figueroa, of Weslaco, Texas,  floored Cannon with a body shot in the first round, then again in the second before referee Vic Drakulich intervened at the 2:08 mark.

Keith Thurman (17-0, 16 KOs) stopped Brandon Hoskins (16-1-1, 8 KOs) at 0:25 of the third round in an eight-round welterweight bout.

In the night's first bout, welterweight prospect and San Diego native Antonio Orozco (14-0, 10 KOs) continued his rise with a third-round TKO of Dillet Frederick (8-6-3, 5 KOs) of Fort Myers, Fla.

-- Bryan Armen Graham