Even ever-courageous Oscar Valdez couldn’t take Emanuel Navarrete’s never-ending assault this time around.

Navarrete relentlessly battered Valdez with an assortment of damaging head shots and brutal body blows, dropped his Mexican rival three times and won their 12-round, 130-pound championship rematch by sixth-round knockout Saturday night at Footprint Center in Phoenix. A well-timed counter left that landed to Valdez’s body sent the former two-weight world champion to the canvas for the third and final time.

Referee Raul Caiz Jr. counted to 10 before Valdez, who writhed in pain, could make it to his feet. The official time of the stoppage was 2:42 of the sixth round.

Navarrete (39-2-1, 32 KOs) retained his WBO junior lightweight title by winning a rematch that took place almost 16 months after he soundly defeated Valdez on points at nearby Desert Diamond Arena in Glendale, Arizona. He re-established himself as one of the most ferocious fighters in the 130-pound division following back-to-back suspect performances that resulted in a 12-round, split-decision defeat to Ukraine’s Denys Berinchyk in his previous fight, which was contested at the lightweight limit of 135 pounds six months after Brazil’s Robson Conceicao fought Navarrete to a 12-round majority draw in their 130-pound championship clash.

A respectful Navarrete credited Valdez (32-3, 24 KOs) for his effort, especially once he was dropped late in the first round thanks to Navarrete’s right hand to the side of his head.

“Look, Oscar Valdez was extremely strong in this fight,” Navarrete told ESPN’s Bernardo Osuna in the ring. “And he kept coming forward, so what I had to do was stop him in his tracks and push him backward. Because if you let Valdez come at you, coming downhill, then it’s gonna be a long night.”

An emotional Valdez tried to come to grips with the first knockout defeat of his 12-year, 35-fight professional career.

“We tried to get the victory,” Valdez, fighting back tears, said to Osuna. “We really wanted it. We trained very hard for this. I’d like to say I’m sorry for all these people who came here to see me from all over the place, from Sonora, from Nogales, from Phoenix. … I wish I could’ve gotten a better result. Thank you for coming here to support. Maybe next time.”

Valdez’s right ankle twisted when he fell awkwardly to the canvas late in the first round. He wasn’t interested in making any excuses for a victory Navarrete clearly earned, though.

“[I] slipped, fell, and kinda messed up my ankle,” Valdez said. “But that’s no excuse. [Navarrete] is a great champion. I take my hat off to him.”

Fast forward five rounds, and Valdez was blasted by another hellacious left uppercut by Navarrete, which knocked Valdez off balance and into the ropes with approximately 1:20 remaining in the sixth round. Valdez valiantly attempted to fend off Navarrete throughout the sixth round, only to have Navarrete nail him with the temporarily paralyzing body blow that rendered him unable to continue.

Prior to his loss inside the distance Saturday night, Valdez had dropped only a pair of 12-round unanimous decisions to Navarrete and unbeaten three-division champion Shakur Stevenson (22-0, 10 KOs).

The fifth round provided evidence of what was to come in the sixth, as Navarrete drilled Valdez with various flush shots. Navarrete’s left uppercut was the most telling blow of the fifth round because it knocked Valdez’s mouthpiece to the canvas with a few seconds remaining in it.

Navarrete’s left hook knocked Valdez backward, into a corner, with slightly more than 1:40 left in the fourth round. Valdez tried his best to make that round competitive, but by then it was obvious that Navarrete regained control of a fight he would win two rounds later.

Several right hands by Navarrete forced a backpedaling Valdez to fall for the second time in their bout, a second before the fourth round ended.

Valdez recovered from a knockdown late in the first round and went blow for blow with Navarrete during a spirited second round. He couldn’t hurt Navarrete, however, and that emboldened the champion to come forward for the remainder of their bout.

Earlier, Navarrete drilled a vulnerable Valdez with a right hand to his temple that knocked him to his gloves and knees with 25 seconds on the clock in the first round. It was quickly clear at that point that this Navarrete was going to be much more difficult to deal with than the lightweight who struggled against Berinchyk (19-0, 9 KOs).

“He was the same old ‘Vaquero,’ ” Valdez said in referring to Navarrete by his nickname. “You know, there’s a reason why he’s a champion. Awkward shots. You know, you don’t see ‘em coming.”

Valdez, who will turn 34 on December 22, didn’t sound like a fighter who sees retirement coming anytime soon, either.

“I really don’t know,” Valdez replied when Osuna asked what’s next for him. “You know, I trained very hard to be a champion. Who knows? Right now, we’re gonna keep our head up high and try to work and work on the mistakes. Whatever’s up, you know, I’m willing to come back, come back strong.”