By Keith Idec

LAS VEGAS – Robinson Castellanos was surprised Yuriorkis Gamboa quit on his stool Friday night.

Nothing about the overall result of their fight surprised Castellanos or his manager, though. They figured Gamboa’s handlers at Golden Boy Promotions picked Castellanos because he has 12 losses on his record, hadn’t fought in 14 months and got knocked out in the seventh round of his previous fight.

None of those factors prevented Mexico’s Castellanos from pulling off a huge upset against Gamboa. The taller, stronger Castellanos dropped Gamboa once apiece in the third and fourth rounds, and he hurt Gamboa multiple times in the seventh round.

The former three-division champion said he was dizzy after the seventh round and he chose not to continue in a scheduled 10-round lightweight bout ESPN2 televised from MGM Grand Garden Arena. Castellanos (24-12, 14 KOs) was ahead on all three scorecards when the fight ended (68-63, 67-64, 67-64).

“I was pretty sure the Gamboa team made a mistake when they chose Robinson as an opponent,” said Enrique Gilbert, Castellanos’ manager. “I thought that maybe they made that decision with the picture of Robinson’s fight against [Oscar] Escandon in mind [a seventh-round knockout defeat]. That was not Robinson.

“Robinson was injured in the chest in first round and he wasn’t able to fight. Robinson has a big heart. He was able to fight until the seventh round, but he wasn’t able to throw his punches. Escandon is a strong guy and I don’t want to disrespect him. He did a good job, but that was not the full version of Robinson.”

Castellanos, 35, hadn’t fought since Colombia’s Escandon (25-2, 17 KOs) knocked him out in the seventh round of their interim WBC featherweight title fight in March 2016 in Washington, D.C.

The 35-year-old Gamboa (26-2, 17 KOs) signed with Golden Boy Promotions in January and had hoped to rejuvenate his stalled career.

The 2004 Olympic gold medalist made an unimpressive Golden Boy debut March 11, when he defeated Nicaragua’s Rene Alvarado (24-8, 16 KOs) by unanimous decision in their 10-rounder in Verona, New York. Gamboa and his handlers attributed that subpar performance to rust, but based on the way he lost Friday’s fight it’ll be extremely difficult to rebuild Gamboa’s career.

“I was surprised Gamboa continued more than three rounds,” Gilbert said. “I was pretty sure Robinson would knock him out. But Gamboa has a good chin. I always hear people say Gamboa doesn’t have a good chin because he gets knocked down every time. But no, it’s because of his footwork. He’s overconfident in his footwork when he attacks. It’s not his chin. It’s the balance.”

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