Trainer Robert Garcia (R) with Floyd Mayweather Jr. Photo by Ed Mulholland/Golden Boy Promotions-Getty Images.

LAS VEGAS — Robert Garcia has been in the opposite corner for unanimous-decision losses to Manny Pacquiao twice, once with Antonio Margarito and once with Brandon Rios.

But as the trainer for WBA titleholder Marcos Maidana (35-3, 31 knockouts), Garcia said that he will be presented with, by far, his greatest opportunity when the Argentine fights RING and WBC champion Floyd Mayweather Jr. (45-0, 26 knockouts) at the MGM Grand on Showtime Pay Per View.

"A fight against Floyd, you know, we're going against the best in history. It is bigger than what I've already been involved in. I've been involved in fights with some of the best fighters in the world, but this is definitely the biggest challenge of my career in the names that we've faced," said Garcia, whose assistant is strength and conditioning guru Alex Ariza.

"Pacquiao has been the best for many years, and I know that he's done a lot and he's accomplished a lot. He's won more titles than Mayweather has, but we've just got to be real. Mayweather is big right now. He's huge. He's, like I said, a lot of people think that he's the best in history. So that, in itself, tells you a lot. He's way, way bigger."

Garcia and Maidana spoke to a group of reporters in the VIP room near the lobby of the MGM Grand. Citing Mayweather's victories over Miguel Cotto and Victor Ortiz by unanimous decision and fourth-round knockout, respectively, Garcia said Maidana would "not respect" Mayweather and would make him "suffer."

"Even though Cotto did good, I think that Cotto waited at times or gave him too much respect. Ortiz was actually fighting the correct way, but he made a lot of mistakes by losing his head and using the headbutt. I think that that was just a way out," said Garcia.

"But I think that the fighter that I have, and the way that we've trained, physically, and, mentally, to go in there and not respect who is in front of him. We know that [Mayweather is] the best in the world, but we also know that he is someone that we can beat. Mayweather has never been in a fight where he has had to suffer and where he's dealing with a hard fighter who has the key to beating him."

Garcia said that he will try to duplicate the effort put forth by Jose Luis Castillo, who lost consecutive unanimous decisions to Mayweather in April and December 2002. Garcia said he thought Castillo deserved the decision over Mayweather during their first meeting.

"A fighter that made him suffer 12 years ago was Castillo. I think Castillo did make him suffer. Most of the time, fighters respect him and they know who he is. They show him too much respect. But 12 years ago, Castillo, I think, was just like Chino right now. He didn't care who he was fighting. Castillo thought that he could beat Mayweather, and a lot of people thought that he did," said Garcia.

"I saw the fight and I thought that Castillo beat Mayweather. If you would have asked me a year ago, I would have said Mayweather won. But I've seen the fight closer round-by-round, and I think that Castillo won the fight. I think in this fight, Mayweather's going to suffer. Mayweather's going to have somebody on top of him that is going to give him a hard time and who is going to make it difficult. It's going to be like a street fight, and I don't think that Mayweather's ever been in a street fight before."

Mayweather was dazed in fights against skillful boxer-punchers DeMarcus Corley and Shane Mosley, although neither could nail him with consecutive or finishing blows.

But Maidana believes strongly that he can do what those two fighters could not.

"It's true, they couldn't land the second punch against Floyd, but when I land and I hurt him, I'm going to finish him," said Maidana. "I'm not going to let him go. I'm going to finish him. I think that I have the chance to knock him out because I hit very hard. Hard enough to knock him out.

"But I can always win a decision. You know, Mayweather doesn't throw that many punches. He throws two or three punches at a time, but very accurate ones. But I'm going to be throwing punches the whole fight for every minute of every round."

Given that his son turned 10 on Tuesday, Maidana said that he would like to reward him with a victory over Mayweather.

"As of now, I still haven't given him anything because I've been very busy. I would like to buy him something," said Maidana. "I would like to give him this win. I know that it will be very difficult, but I would like to give him the win. That would be the best birthday present."