There’s been a lot of trash talk from both sides as the May 2 bout between Floyd Mayweather Jr. and Manny Pacquiao draws closer, but not from the two boxers. It’s the trainers that have been sparring verbally before the fighters are set to meet in the ring.

Freddie Roach has made it no secret that he thinks Pacquiao has the edge with him as his trainer. While preparing his son for the biggest fight of his life, Floyd Mayweather Sr. hasn’t stayed quiet either, indicating that the undefeated boxer will have an easy time because Pacquiao no longer has the punching power that he once possessed.

Mayweather Sr. began training Mayweather Jr. before Roach and Pacquiao linked up, but the Filipino star and his trainer have had a business relationship for longer than the father-son tandem. Roach and Pacquiao first got together in 2001, and they’ve been one of boxing’s best teams in the last 15 years. Mayweather Sr. and his son have had their ups and downs, and they’ve only been together permanently for the past two years.

Other than Pacquiao, Roach has trained other champions in the last 15 years. Most recently, he joined forces with Miguel Cotto in 2013, helping the fighter bounce back from two straight defeats. After wins over Delvin Rodriguez and Sergio Martinez, Cotto has become the best middleweight in boxing.

Roach trained Amir Khan from 2008-2012, helping him get victories over the likes of Marcos Maidana and Zab Judah. Roach also trains Peter Quillin, who remains undefeated following his recent bout against WBO middleweight champ Andy Lee, with whom he fought to a draw on April 11.

An inspirational figure for his battle with Parkinson's disease, Roach, 55, is also considered a brilliant tactician and strategist. Based at the relatively unassuming confines of Wild Card Boxing Gym in Hollywood, Roach finds a way to consistently exhibit a relaxed personality around his prize fighters. Roach's calm temperament could do wonders for Pacquiao's emotions between rounds, in what is expected to be a spirited fight.

“Freddie Roach is the difference,” Cotto told New York Magazine in March. “If Manny follows Freddy’s plan, he’ll be fine.”

May 2 won’t be the first time that Roach will pit one of his fighters against Mayweather Jr. He trained Oscar De La Hoya in his loss against Mayweather Jr. in 2007, and Roach was in his corner for just that one fight. But the fight was the only time that any judge awarded a bout to Mayweather Jr.’s opponent, and Mayweather Sr. has stated that De La Hoya should’ve been awarded the victory.

Roger Mayweather, Floyd Mayweather Sr.’s brother, trained Floyd Mayweather Jr. in his bout with De La Hoya. Mayweather Sr. trained De La Hoya in the early 2000’s, and almost did so against his son.

Mayweather Sr. wasn’t his son’s trainer for some of his biggest fights, but he gets a lot of credit for helping the champ remain undefeated. He’s helped make Mayweather Jr. one of the best defensive fighters in history, allowing him to avoid opponents' power punches and jabs, and remain a top competitor at 38 years old.

Since replacing Roger Mayweather permanently for Mayweather Jr.’s fight against Robert Guerrero, Mayweather Sr. has helped his son win four consecutive bouts. Before the bout in May 2013, Mayweather Jr. hadn’t had his father in his corner in 13 years.  

During the time in which he didn’t train his son, Mayweather Sr. spent time in other boxers’ corners. He trained Ricky Hatton before his IBO light welterweight title defense against Paulie Malignaggi, though Hatton lost the belt to Pacquiao with Mayweather Sr. as his trainer less than six months later.

Mayweather Sr., 62, has spent more time around boxing than almost person in the sport. He previously served as a trainer to former champions Chad Dawson and Joan Guzman, and also the trained Laila Ali. De La Hoya praised Mayweather Sr. for his teaching skills on defense, throwing jabs, and how to be an aggressive fighter. The former champion had also credited Mayweather Sr. for his overall ability to get his boxers in the proper physical condition.

"To me, til this day, Floyd Mayweather Sr. is the best trainer in the world. Hands down," said De La Hoya in 2012.

So, which boxer has the advantage at trainer?

Both trainers have had their share of success. Roach has been on the losing end of a fight against Mayweather Jr., but he’s also been victorious against Mayweather Sr. While Mayweather Jr. is the clear favorite to win the mega-fight, Roach’s success with other boxers proves that he can get more than most out of his fighters, and it should give Pacquiao a slight edge in the corner.