Pacquiao, who started his professional career at 107lb at flyweight, suggested he would not be going any further up through the weights. "This is the last weight division I'm going to fight in and I think my trainer will be happy to hear that because 154 is too big for me and 147 is my regular weight," he said.
Some had claimed this would be the toughest test of Pacquiao's career, and yet Cotto's punches bounced off the Filipino, who nullified his opponent's power and did not apear to get hurt once during the contest.
With a game plan clinically exacted, Pacquiao first lured Cotto into attacking him, soaked up the pressure and counter-punched, and then eased to dominance from the middle rounds onwards. Cotto was down in the third, caught off balance, his hands touching down. But he was hurt in the fourth, hit by a huge left hand. With 13 seconds left in the round, Cotto just survived.
Pacquiao thereafter dominated the stanzas, alternating between sitting back on the ropes and all-out blistering attacks, opening up a cut over the Puerto Rican's left eye.
Pacquiao's slashing attacks in round 12, the final round, caused referee Kenny Bayless to step in to stop the damaged Puerto Rican taking any more punishment after 55 seconds.
Coach Freddie Roach had said that Pacquiao would win through "speed and power", and he was vindicated. Pacquiao certainly remains a special fighter.
Pacquiao (50 wins three losses, two draws) claimed the WBO welterweight title by reducing Cotto to a slow fighter, who could only dance and survive for the last few rounds, until he was stopped in the 12th.
Roach believes a super-fight with Floyd Mayweather would cement the Filipino's legacy. "The whole world wants to see him fight Mayweather and I want Mayweather," Roach said.
Observers ran out of superlatives to describe Mayweather's stunning performance in picking apart Juan Manuel Marquez a month ago at the same venue, and the scene is now set. Who really is the world's No 1 pound-for-pound fighter? Mayweather or Pacquiao.
What is clear is that regardless of the weaknesses of Oscar De La Hoya and Ricky Hatton _ defeated in the last year by Pacquiao – the boxing world has a major fight on its hands. It will require intricate deals, but it is a fight which boxing needs.
Pacquiao now looks capable of stretching Mayweather further than ever before. Expect months of wrangling before an early summer fight in Las Vegas. The world now has a right to know which of the two is the rightful pound for pound No 1.
"My job is to fight in the ring and I think that depends on Bob Arum, my promoter, to negotiate that fight," Pacquiao said.
Pacquiao's place in history
Manny Pacquiao has made history by rising through seven divisions from being World Boxing Council flyweight champion to becoming the World Boxing Organisation welterweight champion.
In that journey, he has won seven world titles. In the last 21 months, Pacquiao has beaten the three No 1 fighters in three divisions – Juan Manuel Márquez for the WBC super-featherweight title, David Diaz for the WBC lightweight title, and now Miguel Cotto for the WBO welterweight title.
That matches Henry 'Melody’ Armstrong Jr, from Missisippi, who went, between 1938-40, from being world featherweight champion through world lightweight champion to world welterweight champion, holding all titles concurrently.