LAS VEGAS — Armando Resendiz outfoxed, outhustled and outmuscled Caleb Plant to score a shocking and well-deserved split decision win Saturday night at Mandalay Bay.

And much like Rolando Romero disrupted future plans for a Ryan Garcia-Devin Haney rematch earlier this month, the heavy underdog Resendiz did the same for Plant’s planned fight against Jermall Charlo, who held up his own end of the bargain by stopping Thomas LaManna in six rounds during the co-main event.

Two of the judges correctly scored the contest 116-112 for the Mexican, while a third surprisingly had it 115-113 for Plant. Resendiz did more than enough to earn the stunning win in a frontrunner for upset of the year.

Resendiz (16-2, 12 KOs) also snatched the WBA interim super middleweight title from Plant (23-3, 14 KOs), who started strong but faded beginning in the fifth.

Armed in the corner with coach Manny Robles, who orchestrated the shocker of the century as the trainer for Andy Ruiz’s 2019 knockout of Anthony Joshua, Resendiz, 26, revived his standing in the sport with a career-best win as a massive underdog.

"I knew that everybody was going to be against me, because on paper, of course, he was the favorite, but I believed in myself," said Resendiz. "My corner believed in me and then we did exactly what we came to do."

Plant came into the clash promising domination, but it was the all-action Resendiz who turned the tables on him, outlanding the American 186-108, sweeping the last six rounds on one judge’s card.

"I felt like it was close and in a close fight, sometimes it switches the other way," said Plant. "I feel like I was in control enough and using the whole ring, using my jab, but the judges saw it the other way."

Plant was calculated to kickstart the contest, largely relying on a crisp jab to keep Resendiz at range.

Resendiz responded in the third and kicked the action into second gear with three hard separate shots — a left hook, a straight left and right hand that rocked Plant, who momentarily held on.

Resendiz carried the momentum through the fourth and fifth rounds and started targeting the body, which surely played a factor as the fight went on.

Resendiz connected with several resounding right hands in the waning seconds of the sixth that badly hurt Plant. He piled on the pressure as Plant held on in desperation. Referee Harvey Dock separated the fighters just as the bell rang, and Plant was saved from perhaps getting dropped.

"It wasn't that he was putting so much pressure on me," said Plant. "He caught me with one overhand right. That was pretty good. But other than that, nothing really hurt me or stunned me … I felt like I did good. I used my jab, I used the whole ring and was patient, but I wasn't the better man tonight."

Plant responded well in the seventh, but it was Resendiz again who was showing more activity, outlanding him 16-8.

Resendiz kept the train of momentum steaming in the seventh and eighth rounds, piling on the pressure with power shots as fatigue started to sink in for Plant, who was throwing one punch at a time.

Action momentarily stalled in the ninth when Resendiz got his glove retaped. He immediately tapped back in, however, to land 27 total punches in the round.

Resendiz's immense activity continued in the 10th as he outlanded Plant 28-9 and clocked him several times with sharp uppercuts.

Plant, known for fading late in losses to Canelo Alvarez and David Benavidez, never caught the second wind in the 11th and 12th rounds like he did in his last fight against Trevor McCumby, a firefight and ninth-round TKO win.

Plant wound up with a small cut over his right eye, and his face was reddened from the heavy leather he absorbed.

"I didn't really worry about what people say. I knew I was going to win," said Resendiz. "I didn't worry at all, knew it was gonna be a tough fight and we gave them a great fight … I'm ready to fight anyone."