Bernard Hopkins
Bernard Hopkins wants to right Floyd Mayweather when he turns 50 years old. Reuters

With four fights remaining on Floyd Mayweather’s Showtime contract, the undefeated boxer appears to be running out of legitimate challengers. He’s set to face Marcos Maidana on May 3, but most experts don’t give the 30-year-old much of a chance.

While few, if any, current boxers have a true shot to beat Mayweather, he has still yet to fight two of the biggest names in recent boxing history. Bernard Hopkins and Manny Paccquiao have both issued challenges, hoping to be one of his next opponents. A bout between Mayweather and either competitor would be a major draw, but neither is likely to happen.

Hopkins has most recently declared his desire to fight Mayweather. The 49-year-old defeated Beibut Shumenov on Saturday to unify light heavyweight world titles. Now, Hopkins has his sights set on the best boxer in the world.

Following his 55th career victory, Hopkins mapped out a plan for Mayweather and him to meet in early 2016. A fight between the two could pit a 50-year-old Hopkins against Mayweather, who would be looking to improve his record to 50-0. Mayweather is scheduled to fight four more times by the end of September 2015, and a victory in each bout would give him 49 career victories, tying him with Rocky Marciano.

"After I become the undisputed light-heavyweight champion of the world, if there was one big fight out there, I know what I would call it -- 50-50," Hopkins said. "He [Mayweather] wants to pass Marciano. He wants to get to 50 and I [will be] 50. That would be huge."

However, too many factors could prevent such a fight from taking place. The most glaring is the weight difference between the two. Hopkins beat Shumenov at 172.5 pounds, and Mayweather won’t weigh more than 147 pounds in his upcoming bout. Hopkins has said he could easily drop to 165 pounds, but Mayweather isn’t likely to take risk his unbeaten record as a middleweight. The most Mayweather has ever weighed for a fight was 150.5 pounds, when he beat Canelo Alvarez in September.

A fight between Mayweather and Pacquiao might be more likely than Mayweather-Hopkins, but that doesn’t mean the mega-fight will ever take place. Even after overcoming issues of drug testing and the split of a potential purse, it looks like the two boxing icons aren’t destined to meet.

The latest hurdle involves Bob Arum and Top Rank. Pacquiao is signed to the promotions company, and Mayweather has vowed to never do business with Arum. The long-time promoter used to promote Mayweather, but the two eventually split. Mayweather later sued Arum.

Even if Pacquiao were to leave Top Rank, many feel that the fight would still never happen. Mayweather is concerned about maintaining a perfect record, and Pacquiao’s camp believes the 37-year-old is ducking a fight with PacMan, because he is afraid to lose. Pacquiao defeated WBO welterweight champ Timothy Bradley on April 12.

After Mayweather-Maidana, Amir Khan looks like the favorite to be named Mayweather’s next opponent. Khan will fight Luis Collazo on May 3, as well.