Pound-for-pound king Manny Pacquiao will defend his welterweight title against former champ Shane Mosley next month, but promoter Top Rank is already making plans for him to fight rival Juan Manuel Marquez in the fall.

Golden Boy Promotions CEO Richard Schaefer said Monday that Top Rank has made a formal, written offer for Marquez, the lightweight champ, to challenge Pacquiao for his welterweight title on a date to be determined in October if he defeats Mosley.

Schaefer said the offer was sent to Golden Boy's attorney by Top Rank's attorney.

Marquez's contract with Golden Boy expired at the end of February. Although Golden Boy has offered him fights and discussed a new deal with him, he has not accepted while holding out hope for a third fight with Pacquiao.

But even though Marquez's promotional deal with Golden Boy expired, the company still has the right to match any offer from another company until February 2012, Schaefer said. He said Top Rank is aware of the matching rights, which is why its attorney sent Golden Boy the offer.

"Last Friday, April 22, Top Rank made a firm offer to Juan Manuel Marquez to fight Manny Pacquiao in October for his WBO 147-pound belt," Schaefer said. "Part of the deal includes a rematch provision in case Marquez would win. So Pacquiao could potentially be tied up for quite awhile."

Schaefer said the written offer to Marquez also contained financial terms, such as the guaranteed purse and the specifics of his share of the pay-per-view profits. Schaefer would not disclose those terms.

Top Rank declined to discuss the offer.

"I have no comment on anything regarding Marquez," Top Rank president Todd duBoef said. "We have said that Marquez would be one of the possible opponents for Pacquiao after the fight with Mosley if he is successful against Mosley on May 7. But I have no comment. I am concentrating on promoting a fight on May 7."

By offering a fight against Pacquiao to Marquez, Top Rank is signaling that Pacquiao will not be facing Floyd Mayweather Jr., this year. Two rounds of negotiations have already failed to produce a deal for that fight, likely the biggest revenue generator in boxing history.

"Based on this offer, it seems like Pacquiao and Top Rank have no interest in fighting Mayweather, at least this year," Schaefer said. "If they did, I am sure Top Rank would have had language in the offer saying this was the deal unless a Mayweather fight could be secured, but it doesn't say that."

Pacquiao, a significant favorite against the 39-year-old Mosley, has already fought two classics against Marquez: a controversial draw in their 2004 featherweight championship fight and a similarly controversial split decision win in their 2008 junior lightweight title fight.

Marquez has been angling for a third fight since, but was passed over in favor of Mosley for the May fight.

The key reason Marquez did not get the fight in May was because when Top Rank was putting together Pacquiao's fight, Marquez was under contract to Golden Boy. Top Rank refuses to do business with Golden Boy and the companies have been embroiled in numerous lawsuits in recent years, including one over Pacquiao's promotional rights, which Top Rank won.