Calzaghe's pummeling of Jones offers a round of lessons

Roy Jones Jr.'s superhuman agility and defense have regressed significantly since his stint in the heavyweight division. DON EMMERT/AFP/Getty Images

As Joe Calzaghe celebrates his legacy-defining victory over Roy Jones, Jr., here's a look at five things we learned from Saturday night's card at Madison Square Garden.

1. For Calzaghe, 175 pounds is a perfect fit.

After making 21 successful defenses of his super middleweight title between 1997 and 2007, the undefeated Welshman reached a crossroads. He'd run out of viable opponents at 168 pounds and, at 36 years old, it was becoming more and more of a strain to make weight.

So Calzaghe moved up to light heavyweight for his U.S. debut against Bernard Hopkins in April, overcoming a knockdown in the first round for a cagey and hard-fought unanimous decision victory. He looked even more impressive in his second outing at 175 pounds against Jones, rallying again from a first-round knockdown -- "It was déjà vu, man!" -- to capture 11 straight rounds and a lopsided decision victory.

Calzaghe has strongly hinted at retirement, perhaps tantalized by the legacy of becoming the second fighter in history to walk away undefeated and undrawn after 40 or more bouts. He's never been motivated by money. But as a competitor, it's hard to imagine Calzaghe retiring after looking so sharp through 24 rounds at the unconquered frontier of 175 pounds. He hasn't sacrificed any of the hand speed or elusiveness with the extra weight and his conditioning remains supreme.

But who would he fight?

There's a rematch with Hopkins, who watched Saturday's fight from ringside and would reportedly consent to a fight in Wales. But the most attractive pairing from a fan's perspective would be Chad Dawson, the undefeated IBF light heavyweight champion. In fact, the 26-year-old southpaw issued a press release just one hour after Saturday's fight -- at 1:25 a.m. on Sunday morning -- congratulating Calzaghe on his victory and offering up a unification fight in the U.K.

When a reporter passed along the information during the post-fight presser, Calzaghe allowed a wry grin.

"I just stepped out of the ring about 15 minutes ago, man. Let me enjoy this fight before I think about fighting somebody else," said Calzaghe. "What do you think I am, a sadist?"

2. Roy Jones, Jr. is finished. (Sort of.)

The longtime pound-for-pound king was the most decorated fighter of his era, but his era has passed. Just two months from his 40th birthday, after getting bloodied and outclassed in Saturday night's defeat, it's clear Jones will not regain championship form.

That doesn't mean the eight-time world champ can't work his way back into another high-profile fight. He's a legend of the sport -- a first-ballot Hall of Famer -- and brings a name recognition to a card rivaled by few other fighters. But his days contending for a mainstream title have passed.

Power is the last thing to abandon a fighter and Jones still has it -- as evidenced in Saturday's first round. But his superhuman agility and defense have regressed significantly since his brief venture into the heavyweight division. And as Jones pushes 40, there's no reason to believe those gifts will return.

It's ironic to think the crowning achievement of Jones' career hastened his decline. Five years ago, Jones gained 25 pounds of muscle mass under the guidance of fitness guru Mackie Shilstone for his heavyweight title bout with John Ruiz. After boxing circles around the overmatched Ruiz and winning a lopsided decision, Jones became the first middleweight to win the heavyweight title in 106 years -- since Bob Fitzsimmons turned the trick in 1897.

But instead of defending the heavyweight belt, Jones jumped back down to 175 pounds, perhaps underestimating the mental and physical toll of boiling down so dramatically at such an advanced age. After all, shedding weight is the hardest thing for a fighter to do successfully.

After winning back the light heavyweight crown with an unconvincing decision over Antonio Tarver, Jones lost three consecutive fights in 17 months. He suffered a second-round knockout at the hands of Tarver in their rematch and, in a frightening scene, was knocked unconscious for several minutes by Glen Johnson. Overmatched in the third fight against Tarver, Jones disengaged and accepted a unanimous decision loss.

Jones bounced back with a string of decision victories over Prince Badi Ajamu, Anthony Hanshaw and Felix Trinidad (who hadn't fought in three years), setting the stage for Saturday's pay-per-view event. But, as Jones discovered Saturday, outfoxing unheralded opponents is much different from contending at the sport's highest levels.