LAS VEGAS — At the end of a tough, long night, Floyd Mayweather Jr. was left staring at a June 1 jail sentence and a boxing landscape that he seems to believe cannot deliver another quality opponent.

The unbeaten 35-year-old champion late Saturday said he’s leaning “80-20” toward retirement.

“If it was my last fight, I gave them a bang,” Mayweather (43-0) said after his unanimous-decision (118-110, 117-111, 117-111) triumph over Puerto Rico’s Miguel Cotto (37-3) at MGM Grand.

“There’s really no one for me to fight anymore.”

Well, there’s Manny Pacquiao, but with the sides divided over money, ego and whatever else they can think up as leverage, who else is there?

The obvious backup to Pacquiao seemed to be Mexico’s 21-year-old Saul “Canelo” Alvarez (40-0-1), who dominated Pomona’s Shane Mosley by unanimous decision Saturday.

But Alvarez’s promoter Richard Schaefer said after the fight he’d just booked the rising star and World Boxing Council super-welterweight champion to headline a Sept. 15 pay-per-view bout at MGM Grand.

With Mayweather’s jail term on a domestic-violence conviction expected to stretch into August — even with time reduced for good behavior — that’s not enough training days.

In addition, Schaefer introduced James Kirkland at the post-fight news conference, with Kirkland saying, “I would love to get that fight,” versus Alvarez.

Alvarez is “interested” in fighting Kirkland, Schaefer said.

“I don’t have to fight if I don’t want to,” Mayweather said. “They say to save the best for last, and if this was my last fight, it was a hell of a fight.”

Mayweather’s swollen face and nose proved that, after he and Cotto spent an hour Saturday exchanging punches in a bout that was more competitive than the scoring indicated.

Mayweather had high praise for his beaten foe’s abilities, which shined most in a gritty eighth round that left the crowd cheering on its feet. He said Cotto fought hard, “but I wasn’t going to succumb to that pressure.”

On a possible Pacquiao fight, Mayweather said, “It’s not going to happen.”

Mayweather’s point is that Pacquiao doesn’t deserve a 50-50 split of revenues, because he contends the Mayweather brand generates more pay-per-view buys. Mayweather earned a record $32 million guarantee Saturday, and that figure will climb.

Mayweather also blames his ex-promoter and Pacquiao’s current promoter, Bob Arum, for complicating the deal after Mayweather promised Pacquiao a $40 million guarantee months ago.

“It’s not my fault,” Mayweather said.

For now, Mayweather said he’ll spend the rest of May visiting with friends and family, taking in his son’s football games and daughter’s gymnastics classes, with the June 1 jail date looming.

“When I go away, I’ll jot down ideas for my company and my sport,” he said.

“You cannot break Floyd Mayweather; you’ve got to know that from when I get hit with those shots in the ring. This is just small time, like training camp.”