Manny Pacquiao speaks with Bernardo Osuna after his unanimous decision victory over Jessie Vargas in Las Vegas and expresses his gratitude to the fans in attendance. (1:13)

LAS VEGAS -- There was high drama before Manny Pacquiao and Jessie Vargas threw a single punch on Saturday at the Thomas & Mack Center.

That is because Floyd Mayweather, the retired superstar, strode to ringside with his daughter during the final undercard bout and took a seat in front of the ringside media, immediately igniting renewed talk of a rematch with Pacquiao, whom he outpointed in May 2015 in the richest fight in boxing history.

But that rematch would not even be discussed without a Pacquiao win. No worries.

With Mayweather, whom Pacquiao said he invited, leaning in and intently watching the fight, Pacquiao stormed to a one-sided decision victory to reclaim a welterweight world title before a wild crowd of 16,132. After the scores of 118-109, 118-109 and a very questionable 114-113 card from judge Dave Moretti in favor of Pacquiao were announced, Pacquiao climbed the ring post with his new belt over his shoulder in front of Mayweather and smiled at him.

Mayweather responded by giving him a thumb's up. Mayweather's comment to the ringside media on Pacquiao's performance: "Not bad."

ESPN.com scored the fight 119-108 for Pacquiao, who was coming out of a brief retirement that followed his lopsided decision win against Timothy Bradley Jr. in April, followed by his winning a senate seat in the Philippines. Now the question is: Will Mayweather join him in returning?

"I'm just taking [my daughter] to the fight," said Mayweather, who does not typically go to fights other than the ones his Mayweather Promotions puts on.

Pacquiao said he came back because he missed boxing and devised a schedule to juggle both jobs. He said he still wanted to make big money, much of which he gives away to the poor in his country. The biggest money would be a rematch with Mayweather. Their fight generated some $600 million. First he had to dismiss Vargas, which he did handily.

"I feel happy," Pacquiao said. "I'm trying every round to knock him down, but I don't want to be careless. I was very careful to go inside because I know he will counter me. I feel I could do more, but every round I did try to knock him out. I wanted to win every round. Walking into the ring tonight as a challenger energized me."

Pacquiao maintained a brutal schedule preparing for the fight. He trained in the morning and at night, with a full day of senate work in between. He fought this weekend only because the date was during a senate recess.

Manny Pacquiao has gone 12 straight fights without a knockout, but he's still an elite fighter to take on the best the welterweight division has to offer. Isaac Brekken/AP Photo

Trainer Freddie Roach was proud of him.

"He worked so hard for me in the gym and so hard for the Philippines in the senate," Roach said. "He had a killer schedule, but one only Manny could complete."

Before the opening bell, Pacquiao looked over at Mayweather, pumped his fist and smiled. After a fairly close opening round, Pacquiao landed a lightning-fast straight left hand that landed flush and dropped Vargas to the seat of his pants late in the second round. He quickly beat the count from referee Kenny Bayless and did not seem too badly hurt.

"Fighting Manny Pacquiao is like playing a very fast game of chess," Vargas said. "You have to be alert at all times. There's a lot of punches coming in. He was very fast, and he was very sharp. His speed surprised me at the beginning, and that [knockdown] woke me up. He has tremendous speed. Fighting Pacquiao only elevated my game, and it makes me better."

Pacquiao, the only fighter in boxing history to win world titles in eight weight classes, kept up an intense attack in the third round, and Vargas looked like a deer in headlights as the crowd went wild with chants of "Manny! Manny!" He was jumping in and out and tagging Vargas with left hands and making him miss badly.

Vargas began to find his footing midway through the fight. There were many exciting exchanges on the inside, and Vargas landed a thudding right hand as the bell ended the sixth round.

"He worked so hard for me in the gym and so hard for the Philippines in the senate. He had a killer schedule, but one only Manny could complete." Freddie Roach, Manny Pacquiao's trainer

The eighth round was action packed as Vargas (27-2, 10 KOs) backed Pacquiao (59-6-2, 38 KOs) up with a right hand before Pacquiao unleashed a flurry. They traded shots, and Pacquiao connected with an overhand right in the final seconds.

Vargas, 27, of Las Vegas, emerged from the round with a bloody gash over his right eye that cutman Rafael Garcia went to work on as soon as the round ended. When Pacquiao nailed Vargas with a right hand in the ninth round, blood went flying from Vargas' wound.

The 37-year-old Pacquiao, the first senator to win a world title, kept the pressure on in the 12th round. He came into the fight having not scored a knockout in 11 consecutive fights since a 12th-round stoppage of Miguel Cotto to win a welterweight title for the first time in November 2009, and he seemed to really be gunning for one. But Vargas was tough and took plenty of hard shots, including a right hand that sent him backward in the final minute of the fight.

"It was a tough fight, but let's give credit to Pacquiao and his legendary performances," said Dewey Cooper, Vargas' trainer. "He is a great champion."

Pacquiao did not come to the news conference after the fight because of the time it took for him to provide a sample for his doping test and because he needed 16 stitches to close a gash he suffered on the top of his head from an accidental head-butt in the 12th round. It came as a surprise that he needed stiches because the cut was not noticeable when it happened since there was virutally no blood.

Pacquiao earned a minimum of $4 million, and Vargas made a career-high $2.8 million for the first defense of the vacant title he won in March with a ninth-round knockout of then-undefeated former U.S. Olympian Sadam Ali. According to CompuBox punch statistics, Pacquiao landed 147 of 409 punches (36 percent), and Vargas connected on 104 of 562 (19 percent).

If Mayweathwer wants a rematch, Pacquiao is certainly interested but did not call him out.

"I'm gonna go back home to the Philippines and back to work in the senate, and then I'll talk to [Top Rank promoter] Bob [Arum] about my next fight," he said. "I don't know who the fight will be. Whoever the people want me to fight. I am not picking an opponent. Whoever my promoter gives me, I will fight. Anybody at 147. [Junior welterweight champion Terence] Crawford at 140? Not a problem."

But what about Mayweather?

"I invited him to come tonight," Pacquiao said.

It would seem clear that there will soon be another invitation, a mutual one from each to meet again, this time inside the ring.