LAS VEGAS — It took just one punch to end the fight.

The legitimacy of the result is another matter altogether.

Guillermo Rigondeaux uncorked a devastating overhand left in an exchange well after the bell to signal the end of the opening round, and that was all she wrote.

Moises “Chucky” Flores took a step back, wobbled, and then fell down in a delayed reaction that some saw as dubious.

After about 10 minutes of conferring between referee Vic Drakulich and Nevada State Athletic Commissioner Bob Bennett, it was ruled a legal blow and a first-round knockout victory for Rigondeaux at 2:59 of Round 1 on Saturday at T-Mobile Arena.

However, Bob Bennett, executive director of the Nevada State Athletic Commission, saw a replay of the KO punch a few minutes later and realized that the officials might’ve gotten it wrong. He said if it can be determined that the punch was thrown after the bell, Rigondeaux would be disqualified.

“He deserves an Oscar,” Paulie Malignaggi told RingTV.com, referring to Flores. “You’d be out right when the punch lands. Because he took a second to go down like that, he’s acting. He even raised his right hand.”

Rigondeaux (18-0, 12 knockouts) retained his 122-pound title, and his status as the best junior featherweight in the world. The ending was marred by controversy, but make no mistake: Flores was going to sleep sooner than later.

The 30-year-old Mexican possessed a massive height advantage, but leaned in and winged wild shots, which the two-time Olympic gold medalist easily picked off.

“It’s not fair. It’s clear that the bell rang,” Flores (25-1, 17 KOs) lamented. “He didn’t throw a punch the whole round. I was winning the round and he waited for after the bell to throw punch when I dropped my hands down.”

The 36-year-old Cuban honed in with his overhand left and couldn’t miss. He landed just nine shots, but the last one — the one that landed after the bell — is all that was needed.

“I commend him for getting in the ring with me,” said Rigondeaux, THE RING’s No. 7 pound-for-pound fighter. “He has more guts than a lot of these other guys. We both threw combinations at the same time at the end of the first round. But mine was quicker and more accurate. It was only a matter of time. I fight to give the best performance to the public and all the fans.

“I am making everyone disappear at 122. I am always available. Tell me who is next. I want all of them, and will take them out one by one. I hope the whole world sees what it is like to get in the ring with me. I am tired of the press and everyone saying I am boring. You see what happens when someone brings the fight to me.”

Indeed, Flores was aggressive and Rigondeaux responded in kind. In his last outing, Rigondeaux shattered the jaw of James “Jazza” Dickens in just two rounds. What Rigondeaux really needs now is opportunity.

HBO’s Max Kellerman floated the idea of superfights at catchweights with fellow pound-for-pound entrants Roman Gonzalez and Vasyl Lomachenko. Rigondeaux says he’s on board.

Now the fights need to happen, once and for all, so Rigondeaux can truly prove his greatness.