The great Manny Pacquiao did everything he could possibly do against Chris Algieri other than get a knockout in a one-sided thrashing to retain his welterweight world title.

Pacquiao, boxing's only eight-division titleholder, scored six knockdowns and dominated virtually every minute of the fight to win a lopsided unanimous decision before a sold-out crowd of 13,201 on Sunday at the Venetian Macao's Cotai Arena in Macau. Now the only question remaining in his legendary career is whether he will ever get fellow welterweight champion and pound-for-pound king Floyd Mayweather Jr. to agree to fight him after years of the biggest fight in boxing going unmade, mainly due to Mayweather's reluctance.

"The people deserve that fight. The fans deserve that fight," Pacquiao said at the post-fight news conference. "It's time to make that fight happen. It's been a long time. I want that fight. They're always denying the fight. I think the fight has to happen."

Coming into the fight with Algieri, there were many questioning where Pacquiao's once-devastating power had gone in recent years because, after a series of crushing knockouts as he moved up the scale, he had not scored one in eight consecutive fights since a 12th-round knockout of Miguel Cotto in November 2009 to win a welterweight title for the first time.

Make that nine in a row now, as the knockout drought continued despite Pacquiao's Hall of Fame trainer, Freddie Roach, predicting an early knockout, even saying at one point that it would be in the first round.

That didn't come close to happening, but Pacquiao (57-5-2, 38 KOs) laid a beating on huge underdog Algieri (20-1, 8 KOs), a junior welterweight titlist who moved up to meet him at a catch weight of 144 pounds. The judges all had it by lopsided decision for Pacquiao, 120-102, 119-103 and 119-103. ESPN.com also had it a shutout for Pacquiao, 120-102.

"Yes. I am looking for a knockout but he is fast and moving, so it's hard to get Chris," Pacquiao said.

Pacquiao's speed advantage was obvious from the opening moments of the fight. He had an easy first round, landing a good straight left hand down the middle and momentarily wobbling Algieri with a right hook.

The 35-year-old Pacquiao, the icon of the Philippines, where he is also a congressman and professional basketball player and coach, connected with a right hook in the second round that began to swell Algieri's left eye. He also landed a left hand that forced Algieri back to a corner, where he slipped on a wet spot. It was ruled a knockdown by referee Geno Rodriguez.

Pacquiao was landing almost at will. He dished out punishment in the fourth round, landing a hard uppercut, lefts to the body and lefts to the head.

Manny Pacquiao easily defended his WBO welterweight title, knocking down Chris Algieri six times. Chris Hyde/Getty Images

Algieri landed some decent straight right hands during the fight, but they had little on them. Algieri was also warned for a low blow in the fifth round.

"I knew he would come on strong," Algieri said. "I had a feeling he would try to blast me out of there just because I'm not used to the big stage. Manny is the best in the world at fighting like Manny Pacquiao. That's really what it is. His style, he has so much experience. He's perfected fighting like Manny Pacquiao.

"The plan was to get to the later rounds without taking too much damage, step up the pace and land shots that would hurt him. If the knockout came, it came. We weren't specifically looking for the knockout, but we were looking to put some damage on the guy."

He never did, and it was Pacquiao putting damage on him. He found his power in the sixth round, knocking Algieri down twice. First, it was a left hand that had Algieri stumbling and then hitting the deck. Then, Pacquiao landed a clean right hand on the chin for the second knockdown.

Pacquiao, who made more than $20 million, scored two more knockdowns in the ninth round, one on a blistering straight left hand that sent Algieri hard to the canvas.