Joe Calzaghe has made the gladiator’s choice, as so many fighters eventually do. He has chosen to risk all he has for a chance at eternal glory.

Everything the undefeated Welshman has achieved the past 15 years, all the things he worked for and dreamed about since he was just a wee boy of 10 when his thoughts were only as large as becoming a British champion one day will be pushed out on the precipice Saturday night when he voluntarily walks into the ring at Madison Square Garden to match fists and wits with Roy Jones, Jr.

At 36, Calzaghe didn’t really need to do this. Certainly the money he hopes to earn had something to do with prodding him to face Jones but the real reason Calzaghe agreed to face the man he considers to be the greatest fighter of his time was about assuring for himself a reputation he knows remains shadowy in many parts of the Byzantine world of boxing.

Calzaghe defended some form of the super middleweight title more times than anyone in boxing history, successfully doing so 21 times over the past 11 years before he moved up to light heavyweight to face Bernard Hopkins in his last outing.

Barely a minute into that fight Calzaghe was on the floor but he did not stay there. He rose quickly and methodically began a 12-round display of boxing that eventually wore Hopkins out and won for Calzaghe the RING magazine light heavyweight title to go along with the 168-pound one he already held.

He could have stopped right there and said “Enough’’ and it would have been. At least in Great Britain it would have. He could have retired unscathed after 45 fights, 32 ending in knockouts despite the suspect hands that have so often plagued and pained him. But something continued to gnaw at Calzaghe and it was something not easily ignored.

People still doubted him, he knew. It is that doubt that the 39-year-old Jones, a man who is a shadow of the fighter he once was but yet perhaps still a shadow too elusive for Calzaghe to climb out from under, understands.

It is also a doubt he intends to exploit if he can Saturday night, using it to force him into mistakes and gambles he has ignored most of his career by reminding him, as he did at the final press conference before the fight on Wednesday, that it is the undefeated fighter who needs the victory, not him.

“This fight has nothing to do with my legacy,’’ said Jones (52-4, 38 KO), who is the first man in 106 years to win both the middleweight and heavyweight titles. “This fight is about his legacy. There’s more pressure on him to win. I’ve already done everything.

“I don’t have to prove anything. I know I’m going to almost have to kill him to take that undefeated record away. If he loses this fight it will tarnish his legacy. The pressure is on him because he’s trying to cement his legacy. I got mine.’’

Indeed Jones has. For many years seen as the best pound-for-pound fighter in the world during the days he was dominating first the middleweight division and then super middleweight and light heavyweight. During those years Calzaghe claimed he wanted nothing more than to face Jones in his prime but the fight never happened, as was too often the case with Jones.

Both sides now lay the blame for that at the feet of Calzaghe’s former promoter, Frank Warren, from whom Calzaghe split after the Hopkins fight after having spent his entire career under his protective (Jones would say overprotective) wing.

Within weeks of that split, Jones and Calzaghe agreed to co-promote this match themselves, Jones because he seems at this late stage of his career unable to walk away from what is becoming a darkened stage. Underneath it all, Calzaghe, meanwhile, seems drawn here because he still knows he has something to prove about himself to a skeptical American public that always tends to look down its flattened noses at European champions.

“Joe Calzaghe was under contract with Frank Warren, right?’’ Jones said. “And he is no longer under contract with Frank Warren, right? When he got out of the contract, what happened? The fight was suddenly made.

“So what does that tell you? Without Frank Warren, the fight got made. So who do you think was the problem? Roy Jones, Jr? Noooo. Was it Joe Calzaghe’s problem? Noooo. It was only one problem and what is the common denominator that is gone now? Frank Warren.’’

Perhaps but now it is Jones himself who is Calzaghe’s problem and even in his lessened state some feel he is the most formidable one of Calzaghe’s long career.

While Calzaghe has tried to deny that, his father and trainer, Enzo, admitted as much earlier this week when he said, “They (American fight fans) put Joe on the back burner. Joe was the first to say to me, ‘Dad, I want to fight Roy Jones. I want to box in America. Dad, I want to box at Madison Square Garden.’’’

Saturday night he will and it will be with much more at risk than the moment. Everything will be at risk for Joe Calzaghe, whose biggest wins to date were a points victory over a 43-year-old Hopkins, a one-sided pounding of vastly over-rated American Jeff Lacy and a similar points win over the Daunted Dane, Mikkel Kessler, that unified the super middleweight titles.

Other than that there are a lot of victories over a lot of men you’ve never heard of and an original title victory over a faded Chris Eubank 11 years ago. Eubank fought only twice more after that and lost both times to Carl Thompson, making clear that he was no longer the man who had battled so evenly with Nigel Benn, Steve Collins and Michael Watson in his younger day.

Because of that, while Calzaghe may be considered one of the greatest fighters in the history of the UK, he remains something less than that in the eyes of the larger boxing public and among the American sporting media. That is why Saturday night he is all in, risking everything he has accomplished in his life because if he loses to an aging Roy Jones many will immediately dismiss him as an accident of boxing’s sad circumstances these days – a guy who won many championships many times but against whom?

“I’m a person who does actions more than words,’’ Calzaghe said this week in his defense. “I’m not going to talk this up more than it has to be. To finish my career fighting at Madison Square Garden is all the motivation I need.

“I’m a guy who wrote Roy off but he came back and won three big fights (after being knocked cold by first Antonio Tarver and then Glen Johnson after first winning the heavyweight title and then dropping back down to 175 pounds too quickly).

“He’s a legend bigger than Hopkins. He’s hungry. He’s in shape. I can’t come in as sloppy as I was with Hopkins.’’

None of that is all that different from what anyone might say in the circumstance Calzaghe finds himself in but then he adds telling words when asked what he thought of Hopkins’ surprisingly dominant defeat of middleweight champion Kelly Pavlik last month.

“We’re not friends but I was happy he beat Pavlik because it showed how big my win was over him,’’ Calzaghe said. “Either I’m doing something right in the ring or they’re all having off days.’’

At first it seems an off-hand comment, a case of self-deprecation. But upon a second reading it seems something more lurks beneath those words. Something deeper and more self-doubting.

It seemed a small admittance, a hint that he knows underneath his 45-0 record lies doubt in the minds of many that nothing he has done to this point has been quite enough to cement his place in the larger boxing world beyond Great Britain’s shores.

So he has now twice come to America to face aging former champions who carry with them large reputations still. He conquered the first when he outpointed Hopkins but he is the first to admit he was not dominating that night and was too often sloppy against a 43-year-old man.

So he is back to try and make his point again in what he insists will be the final fight of his life. Joe Calzaghe, The Pride of Wales, has come into the modern gladiator’s ring to put everything he has ever done on the line for honor.

He is risking it all to prove a point. If he doesn’t do it, he will have proven something else all together. A point he never wanted to make. He will have proven that the doubters and the critics may have themselves had a point all along. As risk goes, it’s a big one.

“Maybe they can see I've made an effort to come over and take on big challenges,’’ Calzaghe said. “A true champion goes outside his comfort zone. I'm away from my country, my environment, my family and friends. It can get tense fighting an American in America, but I wanted to test myself. When I do, I think I perform better.”

He better because Roy Jones is right about at least one thing: the one whose legacy is at risk is not the old guy from Pensacola, Fla. Not by a long shot.