What's left for Floyd Mayweather if he wins again?

Floyd Mayweather returns to the ring tonight on Showtime pay-per-view in just the second rematch of his legendary boxing career, facing Marcos Maidana for the second time. Their first encounter on May 3 of this year turned out to be a better fight and much more competitive than was imagined going in, even though Mayweather won what most agree was a clear if spirited decision over 12 rounds, getting an official majority decision nod from the judges.

Mayweather (46-0, 26 KO) is expected to beat Maidana (35-4, 31 KO) once again tonight, and he's already talking about retiring from boxing in 2015, when he'll be 38 years old. He has two more fights after this one on the record six-fight deal he signed with Showtime and CBS Sports ahead of his 2013 clash with Robert Guerrero, fighting twice each of the last two years.

It's a a standard pace in today's boxing world for star fighters, but unexpected from Mayweather. When the contract was signed, some in the media suspected time would lapse on the deal before we ever saw six fights from Floyd, as he had fought just six times total from 2007-2012, the timeframe in which he became boxing's most marketable bad guy, starting with his fight against Oscar De La Hoya, birthing the "Money Mayweather" persona.

If or when Mayweather beats Maidana in tonight's rematch, what will there be left for him in May and September of 2015? If those are indeed his two final fights, should we expect Floyd to go out in a blaze of big fight glory, or just stay the course and take things in a business as usual manner?

The fight fans' leading candidate, of course, remains Manny Pacquiao. There's no one else at 147 or 154 pounds with Pacquiao's star power, fan base, or accolades, outside of Floyd himself. While it's arguable that there are now tougher matchups at those weight for Mayweather, Pacquiao is still the name that haunts his every step. Despite Manny's knockout loss in 2012 to Juan Manuel Marquez, it's still The Fight. He's working on two straight wins over Brandon Rios and Timothy Bradley, and is expected to dominate in November against Chris Algieri.

Mayweather-Pacquiao in 2015 definitely isn't what Mayweather-Pacquiao would have been in 2010, when the fight came closest to being made. Pacquiao had exploded in stardom at the time, going from a hardcore fan favorite to an international superstar and a box office king due to emphatic wins over Oscar De La Hoya, Ricky Hatton, and Miguel Cotto.

Pacquiao's run of destruction at these weights began in December 2008, so nearly six years ago. That's a long time in a business that, like all sports, is not forgiving of the natural aging process. Manny is undeniably not the same fighter that he was then, though he is still a great fighter. Mayweather, too, has clearly lost a step or two, even though he remains the sport's finest boxer, and probably by a larger margin now than he was then.

The political climate in boxing has not changed enough in the right way for Mayweather-Pacquiao to be any more likely now than it was then, however. Bob Arum's Top Rank still avoids working with Al Haymon fighters, the biggest of whom is Mayweather, and Floyd has not worked with his old promoter since leaving his stable many years ago. While Golden Boy Promotions has changed some this year, with Richard Schaefer's "resignation" and Oscar De La Hoya trying to patch up relations with HBO and Top Rank, that has nothing to do with Mayweather, who does not work for Golden Boy (though he has fought only their fighters for seven years now).

There have again been rumblings of Mayweather-Pacquiao this past week or two, but those rumblings come from Bob Arum, and we've heard this type of thing before. Though there are supposedly negotiations going on, that may just be talk during fight week to keep Pacquiao's name in the news -- in a way, to leech some of the heat from the Mayweather fight. And this is fair, as the reverse has been done in the past by the Mayweather side. Even if it comes off as petty, promoting another fight while boxing is in the news is good for everyone.

But let's assume, as we should, that Mayweather-Pacquiao is not going to happen in 2015. Who are the other possible fighters that Floyd could face in 2015?

Amir Khan has been chasing the fight for years, consistently coming up short when knocking on the door. He thought he had the fight for May of this year, but Maidana's December 2013 win over Adrien Broner pushed him ahead of Amir in the queue. Khan is now hoping to land the fight in May 2015, with a potential December return this year, possibly against Josesito Lopez.

Is Khan the frontrunner for May? Possibly, but there could be a bigger option. If Canelo Alvarez wins another fight in 2014, as he's said he wants to fight again late in the year, he might wind up the third man to score a rematch with Mayweather. Their first fight in September 2013 set revenue records. The biggest impediment there might be that Alvarez may have trouble staying at 154 pounds much longer, and the fact that he was thoroughly routed by Floyd the first time around (despite a crazy scorecard that gave Floyd a majority decision) may make that fight a little less attractive without Alvarez doing something really big late this year.

Or, Canelo could be more likely to meet Floyd in September 2015, which for now looks like it's going to be Floyd's designed final fight.

Other fighters under the Mayweather or Golden Boy banner who could be interesting options are Keith Thurman, a rising welterweight contender who has power and skill, and Danny Garcia, the reigning king at 140 pounds, who is likely moving up in weight soon. Kell Brook, who fights for Matchroom Boxing, is the new IBF welterweight titleholder, and could be an outside contender for a Mayweather fight next year.

There's also another idea for a rematch, one with Miguel Cotto, who is the current middleweight champion of the world. That would give Floyd a chance to fight, perhaps at a junior middleweight limit of 154 or a catchweight of 155, for a world title in yet another weight class. Mayweather beat Cotto in 2012, an interesting fight then that might be better now, as Cotto has been retooled under trainer Freddie Roach. Though Miguel has been working with Top Rank of late, he's not signed there, and promotes himself. Thus, he's free to fight who he wants, and Cotto has been adamant about going where the money is.

What's the most interesting scenario? It might be Cotto and Canelo, a pair of fights at 154 pounds, rematches that pit Mayweather against a former strong rival in Cotto, or a top young star (still) in Alvarez. You can sell Cotto as better than he was in 2012, reawakened under Roach. You can sell Alvarez as having learned from his loss to Floyd in 2013, better prepared for the fight this time, and with Mayweather two years older.

Is there danger out there? There's no fight Mayweather can or is likely to make that would see him as an underdog, or even less than a pretty heavy favorite. In that respect, Mayweather will likely go about what may or may not be his final two fights in a business as usual sense. But first up, he has to win tonight. And he almost surely will, just like he's done 46 other times.