Las Vegas, NV (SportsNetwork.com) - Floyd Mayweather Jr. kept his perfect record intact by soundly beating Manny Pacquiao in the "fight of the century."

Mayweather (48-0, 26 KOs) became the unified welterweight champion with a 12- round unanimous decision Saturday night in the long-awaited meeting between two of the best pound-for-pound fighters of their generation.

The 38-year-old won by scores of 118-110 from judge Dave Moretti and 116-112 from Glenn Feldman and Bert Clements.

The 36-year-old Pacquiao (57-6-2, 38 KOs) could never get past the strong defense from Mayweather.

"I did my best, but my best wasn't good enough," Pacquiao said in the post- fight news conference. "I thought that I won, but I have to review it on DVD."

Mayweather, who said he earned upwards of $200 million for the bout, was the odds-on favorite to win. The finish was what many had expected, a Floyd victory via decision in front of a crowd filled with stars at MGM Grand Garden Arena for the richest fight ever.

The hefty pay-per-view demand caused an overload to many cable systems in the United States due to people ordering the fight in droves, with a price up to $100 for the event.

The fight was expected to produce as $400 million in revenue between gate receipts and pay-per-view purchases, easily the highest-grossing fight in boxing history.

Deep into the post-fight press conference, Mayweather announced he would relinquish the WBC, WBA and WBO titles in a couple of weeks and said, "I think my last fight may not be a championship fight."

He also said his decision to give up the titles was to "give other fighters a chance."

Upon walking out of the post-fight press conference, Mayweather showed off his $100 million check delivered to him.

It was also during the post-fight news conference, Pacquiao and his camp acknowledged he injured his right shoulder in training camp. He took anti- inflammatory shots that were approved by the U.S. Anti-Doping Agency in the lead-up to the bout. Pacquiao requested to get another shot a few hours before the fight, but that was denied by the Nevada Athletic Commission.

Freddie Roach, Pacquiao's trainer, said his camp thought about postponing the fight due to the shoulder injury, but they thought the progress was good enough in the days leading up to it.

Pacquiao admitted the shoulder injury prevented him from following up on punches and making combinations during the bout. Roach said because of the shoulder injury it was hard for Pacquiao to throw a hook.

"Athletes always fight hurt," promoter Bob Arum said. "We thought the work that was done on the shoulder during training would give him the opportunity to use his right hand."

Arum admitted Pacquiao's injury got worse after the third round.

After the fight, which Mayweather won handily on punch connection count (148-81), the pound-for-pound king stated he would fight one more time under the contract he signed with CBS/Showtime in 2013. A win in his next bout would tie the mark of Rocky Marciano, who has the most wins for an undefeated champion.

"My last fight is in September and then it's time for me to hang it up," Mayweather said as a number of boos rained down from the crowd.

Later, during the post-fight news conference, Mayweather said "my love and my passion for boxing is not the same the way it once was."

He also admitted that he contradicts himself, so maybe there will be more than one fight in Mayweather's future.

Pacquiao, who said during an in-ring post-fight interview, stated he would go on vacation and then decide on his next plans, which ultimately may include surgery due to the shoulder problem.

There were no knockdowns and very few combinations landed that would lead to one staggering.

The fighters had a very different take on how the bout went after it was completed.

"He's a tough competitor. I'm just very fortunate to be where I'm at. Manny Pacquiao is a much smarter fighter than I thought," Mayweather said.

The defense of Mayweather seemed to be Pacquiao's ultimate downfall, but the Filipino star was disappointed in the scoring.

"I thought I won the fight. He didn't do nothing, but move outside," Pacquiao said in a post-fight interview in the ring.

Pacquiao said he thought he was up in the fight and that's why he didn't go on the offensive in the final few rounds.

Mayweather came into the fight holding the WBC and WBA welterweight belt and Pacquiao, the only boxer to capture world titles in eight different weight divisions, owning the WBO welterweight crown. It was the jabs and footwork of Mayweather that was the difference Saturday night. Also, Pacquiao connected on only 19 percent of his punches, compared to 34 percent for his counterpart.

Pacquiao landed only nine percent of his jabs and Mayweather hit on 25 percent of his jabs.

Mayweather dominated the first three rounds, but Pacquiao got the better part in two of the following three rounds. The fourth round looked like a turning point for Pacquiao when he backed Mayweather to the ropes, but his ability to cover up using his gloves kept Pacquiao at bay.

In the sixth round, Pacquiao again had tremendous energy and backed his foe to the ropes, but Mayweather shook his head side-to-side as if to say "No, no, the punches aren't hurting me."

Mayweather threw and landed enough jabs to keep Pacquiao away and in the final round Mayweather raised his right glove in the closing seconds to signal he was well ahead on the scorecards.

As part of the undercard, Vasyl Lomachenko kept his WBO featherweight title with a ninth-round knockout of Gamalier Rodriguez.

Lomachenko (4-1, 2 KOs), making the second defense of his belt, floored Rodriguez (25-3-3, 17 KOs) in the seventh round and again in the ninth. Rodriguez was counted out 50 seconds into the ninth round.