There are a number of reasons why Manny Pacquiao and Floyd Mayweather have never stepped in the ring together. While some of the issues between the two fighters have been resolved over the years, one obstacle still stands in the way.

As long as Pacquiao is signed to Top Rank, fans aren’t likely to see Mayweather vs. Pacquiao. Mayweather refuses to work with Top Rank, because of CEO Bob Arum. Arum promoted Mayweather until 2006. Two years later, the undefeated boxer sued the promoter, claiming he wasn’t paid what he was owed for fights against Arturo Gatti and Zab Judah.

Mayweather has stated that Pac-Man would have to leave Top Rank, in order for the two sides to agree upon a bout. Pacquiao, though, has said that he won’t break from the company to satisfy Mayweather.

“Floyd Mayweather Jr. never runs out of excuses just to avoid fighting me. If I leave Top Rank, there’s no guarantee the fight would push through,” Pacquiao told the Inquirer in January. “So, why should I leave Top Rank? Just to make Pacquiao-Mayweather fight happen? No way.”

Pacquiao advisor Michael Koncz told the L.A. Times that he’s not even thinking about a fight with Mayweather. On April 12, Pacquiao has a rematch set with Timothy Bradley. According to Arum, the winner will go on to face whoever comes out on top in the Juan Manuel Marquez-Mike Alvarado bout.

With Top Rank, though, Pacquiao appears to be running out of potential opponents. If he goes on to face Marquez, it will mark the fifth time that the two have fought. They last met in December 2012, when Marquez knocked out Pac-Man, picking up his first victory in their rivalry.

While Pacquiao won’t leave Top Rank because of Mayweather’s demands, there’s no guarantee that he’ll remain with the promotion next year. His contract runs through 2014, but he has yet to re-sign with the company. In February, there were rumors that Pacquiao had agreed to stay with Top Rank for two more years, but that has been denied.

“There has been no extension of Manny Pacquiao’s contract with Top Rank,” read a statement on Pacquiao’s official website. “To hopefully stop all the rumors, we are making an official statement that no contract extension between Manny Pacquiao and Top Rank for a reported $75 million.”

The original proposal for a Pacquiao-Mayweather fight never came to fruition, because of Pacquiao’s refusal to take a blood test. The two camps have also quarreled over the split of the purse.  

Mayweather will fight Marcos Maidana on May 3. He's scheduled to fight again in September.