LAS VEGAS — Neither the moment nor Canelo Alvarez were too big for Terence Crawford.

Two years after he tore through Errol Spence to become undisputed welterweight champ, Crawford upset Alvarez to accomplish the same feat in a division capped 21 pounds higher.

It was a much more measured performance from Crawford, but he outboxed Alvarez solely from a southpaw stance and unanimously won a 12-round, 168-pound championship clash Netflix streamed worldwide from sold-out Allegiant Stadium.

Judges Tim Cheatham (115-113), Max De Luca (115-113) and Steve Weisfeld (116-112) scored for Crawford, who cried after Michael Buffer announced him as the winner.

Crawford’s career-defining victory occurred in the biggest boxing match held in the United States since Floyd Mayweather beat Manny Pacquiao by unanimous decision in their welterweight title fight 10 years ago at nearby MGM Grand Garden Arena.

Crawford (42-0, 31 KOs), who will turn 38 in two weeks, became a world champion in a fifth division before a capacity crowd of 70,482 and further cemented himself as a generational great. He is also the first male boxer in the four-belt era to be crowned undisputed champion in three weight classes (junior welterweight, welterweight and super middleweight).

The Omaha, Nebraska, native accomplished what was commonly considered unthinkable a couple years ago by beating a hard-hitting, longtime super middleweight who cleaned out the 168-pound division when Crawford was the WBO welterweight champ.

Crawford, who ended a 13-month layoff, often fought off his back foot, took Alvarez’s power well when he got caught and picked his spots to trade with an opponent who won a light heavyweight title bout by knockout in November 2019.

“Canelo is a great champion,” Crawford told The Ring’s Max Kellerman following his impressive win. “I’ve got to take my hat off to him. He’s a strong competitor. I’ve got nothing but respect for Canelo. I’m a big fan of Canelo. He fought like a champion.”

Alvarez, 35, lost his Ring, IBF, WBA, WBC and WBO titles to a perceived smaller fighter who moved up 14 pounds from the junior middleweight division to challenge him. OnlyMayweather, Bivol and Crawford have defeated Alvarez (63-3-2, 39 KOs) during the Mexican legend’s illustrious 19-year career.

“I feel great,” Alvarez said. “First and foremost, I want to thank everyone who came to support and has always been behind me. I’m a winner for being here. There is no defeat here. I’ve done everything in my career. I’ve come to take risks, and that’s what I did.”

Crawford, who is ranked third pound-for-pound by The Ring, outlanded Alvarez by 16 punches, according to CompuBox’s unofficial stats. CompuBox counted 115 of 534 punches for Crawford and 99 of 338 for Alvarez, who landed more power punches (83 of 260 to 70 of 208).

“Crawford is a great fighter, a skilled fighter,” Alvarez said. “And I give the credit to Crawford, obviously.”

It seemed by the time the final round began that Alvarez needed a knockout to win.

Crawford’s combination caught Alvarez 30 seconds into the 12th round. A left hand by Crawford turned Alvarez’s head around barely a minute into it.

For good measure, Crawford clipped Alvarez with one last left hand that knocked him off balance when there were five seconds left.

Unlike most rounds, Crawford stayed in the pocket and traded with Alvarez in the opening minute of the 11th round. Crawford connected with a right hook to the body and a straight left to the head. Alvarez expressed frustration when Crawford stung him with a jab at the halfway point.

Alvarez’s right hand knocked Crawford off balance a little less than a minute into the 10th. Another short right by Alvarez landed with just over 1:20 to go.

After failing to engage much in the eighth, Crawford unloaded right hooks and left hands in the opening 20 seconds of the ninth. Alvarez exchanged with him, but Crawford was more effective and landed 33 punches in those three minutes, by far the most in the fight to that point.

With his back to the ropes, Crawford tried to tie up Alvarez. Their heads collided as they wrestled for position and a small cut opened above Crawford’s right eye.

It had no impact on the outcome.

Crawford opened their fight in a southpaw stance and mostly moved away from Alvarez in the first two minutes. He landed a left-right combination with just under a minute to go however, which temporarily made Alvarez stop coming forward and should’ve won him a round that lacked action.

Eleven rounds later, Alvarez addressed losing a showdown he initially resisted because he felt he wouldn’t get credit for winning because Crawford came up so much in weight.

He also addressed the possibility of a rematch.

“I feel great to share the ring with great fighters like him,” Alvarez said. “If we do it again, it’s going to be great. I’m glad to share the ring with great fighters. I’m glad to be here. I already did a lot in boxing. I already accomplished a lot in boxing. My legacy is already there, and I am still taking risks because I love boxing.”

Alvarez lost for the first time at super middleweight in 12 bouts.