Ricky Hatton improved to 43-0 with 31 knockouts. (Getty Images/Ethan Miller)

Ricky Hatton improved to 43-0 with his 31st knockout tonight, dropping Jose Luis Castillo in the fourth round with a perfectly-placed left hook to the liver that ended the fight and, possibly, the important part of Castillo's long career.

Castillo (55-8-1) will probably fight on if for no other reason than he's in debt and is being sued by the estate of Diego Corrales for failing to make weight in their second fight and the aborted third fight. But this loss was a devastating blow to Castillo's current standing in the boxing world, as he was overmatched and overpowered by the younger, stronger Hatton from the opening bell.

Castillo never seemed like he was in the fight, with Hatton's bully style overwhelming him. Hatton consistently hit first, and wound up outworking and outlanding Castillo rather significantly. Much of the action took place inside, with Castillo and Hatton both clinching a lot and sometimes fighting out. But it was Hatton landing his left hook and his uppercuts, and Castillo only able to land shots while the two were entangled, or occasionally in counter to Hatton's punches.

Some are going to go ahead and say that Hatton still hasn't proven anything, and it's true that Castillo looked washed-up, warmed-over, shot -- whatever you want to use. But he did beat Castillo with ease, and Castillo is still a quality fighter, if not the guy he used to be. Hatton couldn't have done much more than sign a fight with Jose Luis Castillo and beat him, and he did that. He took on a highly-regarded, popular fighter, made good money, and came away with another win.

We all know what's probably next for Castillo. Some fights he can win, maybe some fights against up-and-coming fighters that he can't. But how about Ricky Hatton?

Hatton wants Floyd Mayweather, Jr. -- badly. But Floyd won't fight Hatton, because there's not enough money in it. Hatton is a star in America, and he's a megastar in England. To Mayweather, however, he's just another inferior boxer who (in his own mind, at least) can't present him with a challenge worth his while. And, again, the bottom line is that the huge bucks aren't there unless they were to fight in England, which isn't happening.

With Floyd a huge reach for Hatton and his camp, Jim Lampley raised the question of whether or not Hatton should step back up to the welterweight division. It would be a huge mistake. Hatton struggled mightily against Luis Collazo last year, and it was completely agreed upon that 147 was not the weight for Ricky Hatton. Now we're discussing whether or not he should go back to fight a guy like Cotto, Margarito, Williams, or Mosley? Come on. Collazo is tough, but he's a second-tier welterweight, and Hatton had enough trouble there. If he could get Floyd at 147, I'm sure he'd take it. Otherwise, I don't know that he'd see the point.

For Hatton, 140 is the weight. So assuming he stays there, who's next? Junior Witter is the fight that a lot of people want, and it would do a huge live gate in England. But Ricky wants to fight in Vegas, where Hatton/Witter wouldn't be the same draw or have the same atmosphere. And Hatton still has no intention of fighting Witter last anyone heard, so count that out.

Vivian Harris, who was rumored to fight Witter this summer, is another name. It could be a good fight, with Harris' power, height and reach possibly neutralizing Hatton's rushing style.

Demetrius Hopkins is out there, but he's a turd and I don't want to see Hatton waste his time with a guy who's getting by because of his promotional company and his last name. The winner of Ricardo Torres v. Kendall Holt could be intriguing. And HBO would be really high on a matchup between Hatton and recently-crowned IBF champion Paulie Malignaggi.

There are other good fighters in the division -- Souleymane M'baye, Andreas Kotelnik, Juan Lazcano -- but none of them would be able to sell a fight in the States, and these just aren't the days where Hatton fights on anyone's undercard.

It's up in the air who next fights Hatton -- my money's on Malignaggi, which will be jumping the gun on Paulie's career. Whoever it is, it's unlikely to make Hatton any bigger of a star than he is right now. The win over Castillo was splashy and will make boxing headlines, no matter what stage of his career Castillo is at now. For now, no big star is in Hatton's future. But there are good fights out there. He just has to take them, and I think we can count on Hatton to do that.