Everyone knows guys like to compare sizes.

Alright, I admit it, girls like to do it too.

What I'm talking about, of course, is the potential for an oft-rumored "superfight" between UFC welterweight champ Georges St. Pierre and UFC middleweight champ Anderson Silva. Although this is a fight that has been literally talked about for years, the discussion now seems to be increasingly centered around the size of the contestants.

Or more precisely, their weight.

As recently as a couple of weeks ago, UFC president Dana White was talking about the fight as a near certainty if only St. Pierre could get past interim champ Carlos Condit on his return after a long injury layoff. Silva had been vocally promoting the match-up, and St. Pierre, although focused on Condit, was saying that he was looking for "bigger and better challenges" in the future. The fight would be held at a catchweight if it happened to minimize size differences between Silva and St. Pierre, either 175 or 177 pounds depending on who and when you asked.

Seems simple, right?

Not so fast.

After retaining his title against Condit at UFC 154, a battered St. Pierre remained non-committal about the challenge from Silva, bringing up the difference in size between himself and the middleweight champ several times. So just how easy- or how difficult- will it be to find a middle ground where these two will agree to meet?

Apparently, not too easy.

"If Anderson came down to 170 pounds, we'd say yes, 100 per cent, certainly," St. Pierre's trainer Firas Zahabi recently told Sportsnet. "But if we're asking Georges to fight in a higher weight category, it's another story."

"If the bigger guy challenges the smaller guy," Zahabi added, "it's him who should come down a weight category."

Now we are talking about a title fight at welterweight instead of a catchweight. A very big difference indeed. Is it too much of a difference to be realistic? 

Although Silva began his career as a welterweight, he hasn't seen 170 pounds in competition in the past nine years. In the time since, Silva has made his mark as the most devastating middleweight fighter the sport of MMA has ever seen, with occasional forays up to light heavyweight that all resulted in first-round knockouts of his opponents. Normally on fight night he enters the Octagon weighing a little over 200 pounds, lighter than the 220 or so he carries around between training camps when he's not in fighting trim. It's questionable if Silva could even safely cut down to 170 pounds now if he wanted to, or if it would be in his best interest to go through the nutritional and diet regimen necessary for him to shed the mass necessary to make the cut.

St. Pierre, on the other hand, has spent his entire career fighting at welterweight, and for the last five years dominating every fighter in the division as UFC champ. It's a weight class he knows inside and out, and although in the past he has spoken of possibly moving up to middleweight, in recent years he has backed away from that idea. St. Pierre is a master at cutting weight, entering the cage on fight night weighing around 193 pounds, about the same as he normally weighs between fights. Interestingly, his reach is almost identical to Silva's, despite their four inch difference in height- only about one inch less.

The weight difference between the two, fighting weight at least, is not as great...