By Keith Idec

LAS VEGAS – Yuriorkis Gamboa can’t use rust or a long layoff as an excuse for this.

Less than two months after a lackluster performance in his return from a 14-month layoff, Mexico’s Robinson Castellanos stopped Gamboa after the seventh round of their nationally televised fight Friday night. Castellanos floored Gamboa once apiece in the third and fourth rounds and appeared to hurt the former three-division champion more than once in the seventh round at MGM Grand Garden Arena.

Gamboa told his corner men he didn’t want to continue following the seventh round and they told referee Russell Mora to stop the fight. The 35-year-old Gamboa, a 2004 Olympic gold medalist from Cuba, lost for just the second time as a pro and for the first time since Terence Crawford stopped him in the ninth round of their lightweight title fight nearly three years ago in Omaha, Nebraska.

Gamboa was down on all three scorecards when the fight ended (68-63, 67-64, 67-64).

The technical knockout defeat ruined Gamboa’s comeback with Oscar De La Hoya’s Golden Boy Promotions, which signed him in January and tried to lead the talented, enigmatic ex-champion back to prominence.

Mexico’s Castellanos (24-12, 14 KOs) pulled off a huge upset in a bout broadcast by ESPN2 and made the most of his debut at lightweight after boxing almost exclusively at featherweight during his 15-year pro career. Before Friday night, the 35-year-old Castellanos hadn’t fought since Colombia’s Oscar Escandon (25-2, 17 KOs) knocked him out in the seventh round of their interim WBC featherweight title fight 14 months ago in Washington, D.C.

“I am super happy and excited to get such a big win,” Castellanos said. “I won against a revered Olympian, and this win puts my career back on track after my last fight. This win is the opportunity that I needed, and it’s because of the incredible team around me.”

Castellanos buckled Gamboa’s knees with a left hook late in the seventh round, which might’ve led to Gamboa believing it would get worse in the eighth.

Earlier in the seventh, Castellanos caught Gamboa with a flush uppercut and added a hard right hand before Mora could break them up near the ropes. Gamboa came back to clip Castellanos with a straight right hand before the midway mark of the seventh.

Gamboa survived a knockdown apiece in the third and fourth rounds and began mounting a comeback in the fifth round. He looked better in those three minutes than he had in the first four rounds, when it looked like he would get knocked out.

Castellanos connected with a right hand that dropped Gamboa less than 30 seconds into the fourth round. Gamboa apparently hadn’t recovered from getting knocked down late in the third round, yet reached his feet again and began exchanging with the taller, stronger Castellanos.

Castellanos made Gamboa pay for showboating earlier in the bout by drilling him with a counter right hand that floored Gamboa late in the third round. Gamboa got up, but the bell to end the round sounded just as Mora motioned for them to resume the action.

Gamboa went down less than 10 seconds into the third round, but Mora determined it wasn’t the byproduct of one of Castellanos’ punches. Castellanos landed a few right hands from long distances during the first two rounds, but Gamboa took those well.

This TKO loss was a second straight poor performance from a fighter once considered one of boxing’s best. Gamboa beat Nicaragua’s Rene Alvarado (24-8, 16 KOs) by unanimous decision in their 10-rounder March 11 in Verona, New York, but he looked rusty and sluggish in what was his first fight since December 2015.

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