(CNN) - Keith Thurman vowed to end Manny Pacquiao's career but it was the Filipino boxing legend who taught his younger rival a lesson in Las Vegas.
The 40-year-old set the tone by flooring Thurman in the first round with a straight right hand and won the 12-round bout on a split decision to become the oldest welterweight champion in history.
Pacquiao seemed to have the clear advantage Saturday but one ringside judge, Glenn Feldman, gave the 30-year-old American a 114-113 advantage.
Dave Moretti and Tim Cheatham, though, both scored it 115-112 to Pacquiao.
Thurman lost for the first time (29-1) while Pacquiao collected a 62nd victory (62-7-2) and said it wouldn't be his last fight, either.
To that end, could a rematch with Floyd Mayweather be on the cards? That has been discussed for a while. Mayweather, one of those looking on at the MGM Grand, would need to come out of retirement first.
The fighter nicknamed 'Money' -- who last fought two years ago -- beat Pacquiao in a unanimous decision in 2015.
Although the bout failed to live up to expectations, it was a money spinner indeed with Mayweather pocketing a reported $250 million.
On Saturday, Pacquiao's quick start rattled Thurman, who recovered in the middle rounds and even punished his opponent in the ninth.
Pacquiao, though, responded in the 10th round with blows to the body and Thurman couldn't produce the big finish he realistically needed in the 12th.
"It was fun," Pacquiao, a titlist in a remarkable eight different weight classes in his career, told the crowd. "My opponent is a good fighter and boxer. He was strong.
"I think he did his best, and I did my best. I think we made the fans happy tonight because it was a good fight."
Thurman, slowed by hand and elbow injuries in recent years, said Pacquiao just had too much for him.
"I wish I had a little bit more output to go toe to toe," he said. "My conditioning, my output was just behind Manny Pacquiao's tonight.
"Tonight was a blessing and a lesson."