Rancorous breakups in boxing have the potential to sully the reputation of even the most accomplished performers.

Only two years ago Mikkel Kessler was identified by many observers as the likely slayer of “Italian Dragon” Joe Calzaghe. Wales’s world super middleweight champion was almost 36 years old and deemed to be ripe for the picking by a bigger, stronger, younger and ambitious rival. Kessler lost on points – no shame given that he performed impressively against a future Hall of Famer – but then he lost momentum. His next two opponents were Dimitri Sartison and Danilo Haussler. Frustrated, he split from Danish promoter Mogens Palle and joined Wilfried Sauerland’s stable in Germany, a move that cost him 11 months out of the ring. The acrimony was eclipsed only by a perception that post-Calzaghe his career had gone the wrong way.

But the 30-year-old “Viking Warrior” maintains that he is still one of the elite practitioners of his profession, a conviction he intends to reinforce in the forthcoming Super Six super middleweight tournament bankrolled by Showtime TV. Americans Andre Ward and Andre Dirrell (the former of whom Kessler is scheduled to face in the first phase of the round-robin series in November) are unproven. Carl Froch, the WBC titleholder from Britain, is tough and unyielding but defensively flawed and vulnerable (all of which was emphasized in a captivating bout against Jermain Taylor in April). Taylor has been brutally stopped twice by Froch and Kelly Pavlik. And Arthur Abraham, the former IBF middleweight titleholder, is dangerous and unbeaten but not established at 168 pounds. Which leaves the Dane in the driving seat.

“Kessler is unquestionably the favorite in this tournament,” said Teddy Atlas, ESPN’s boxing analyst. “That doesn’t mean he is going to win but, clearly, he is the man at 168 pounds. He fought very well against Calzaghe, lost a decision, but he had great moments in that fight. He probably does everything a little better than most of these other fighters in this tournament but can he remain consistent at this level against these fighters and still win the tournament? The thing about this tournament that makes it so unique is that very few fighters will face this level of competition on a sustained basis over the course of 18 months to two years. You must win four fights in a row to take the prize and, based on that kind of competition, you just don’t know how any of these guys will respond, Kessler included.”

But Kessler, who will defend his WBA belt against overmatched Venezuelan Gusmyr Perdomo Saturday in Herning, Denmark, is a more authentic commodity at super middleweight than any of his rivals. As an amateur, Kessler won 44 of 47 bouts and secured multiple Nordic titles. He left school at 16 to work as a mechanic with Mercedes-Benz, an apprenticeship he never completed. It was not that he lacked dedication – neither of his parents had much money, so he had held down a variety of jobs from boyhood, including paper rounds, waiting in restaurants, dishwashing, even working in a kindergarten and nurserey school – but boxing enraptured him. When it came down to a choice between a career as a mechanic or the offer to turn professional with Palle as his promoter, Kessler did not think twice.

He made his debut in 1998, won a six-rounder on the undercard of Mike Tyson-Brian Nielsen (and Calzaghe-Will McIntyre) in October 2001 and in his 30th bout he outpointed South African Dingaan Thobela, remarkably a former titleholder at lightweight and super middleweight. In the boxing world, Copenhagen is no citadel, so Kessler’s record had to be built up slowly. But when his big opportunity arrived five fights later against Puerto Rican Manny Siaca, he took it with both hands, demonstrating the polished defensive skills and powerful offense that had become his forte. Siaca quit at the end of the seventh round, surrendering his WBA belt to Kessler, who was 35-0 with 27 stoppages. Within three years – after successive wins over Anthony Mundine in Australia , Eric Lucas and Markus Beyer (both shopworn) and the hard, but limited Librado Andrade – he was Calzaghe’s heir apparent and, although it was not to be, he gave the Welshman the fight of his life. Calzaghe never performed better under pressure. Kessler could be philosophical in defeat.

“My only regret about the fight against Calzaghe is that it did not lead to a rematch – Joe ruled this out, saying he didn’t want to face me again – or to an encounter with some big-name Americans such as Bernard Hopkins or Kelly Pavlik,” Kessler reflected. “These were the kind of opponents I wanted to meet and it was frustrating when none of these matches could be made. But this is the politics of boxing. I met Hopkins and we shook hands but there was no deal. That’s why I’m excited about the Super Six tournament because I want to test myself always and this is a great opportunity to shine the spotlight on the super middleweight division.

“Of course, I’m not thinking about the Super Six or Andre Ward right now. I’m focused on Perdomo and I’m happy to be getting back in the ring. I want to take my WBA belt into the tournament, so with Perdomo being my mandatory challenger, he is an obstacle I need to overcome. Then I can begin to concentrate on other challenges that lie ahead, challenges that will get me excited and will excite the fans, too.”

The threat of legal action by Palle – who suggested that his former charge was hijacked by “pirates” – has been dismissed by Sauerland Event.

“Mikkel’s former promoter can sue all he wants, he is not going to get a legal contract through that,” said CEO Kalle Sauerland. “Neither Mikkel or ourselves or Showtime have violated anyone’s rights. Palle can sue whomever he wants but it does not give him any options or any rights over Mikkel Kessler at all. He simply does not have a valid contract with Kessler.”

Ultimately, Kessler’s validity will be defined by what he achieves in the ring over the next few years, and Calzaghe, for one, anticipates that he will accomplish plenty.

“Kessler can dominate the super middleweight and light heavyweight divisions, he has the class to rule, no question,” Calzaghe said. “He is a class act, a very strong man at the weight and an accomplished boxer. I really had to dig down deep to beat him and, unquestionably, it was my best-ever performance. His jab is a formidable weapon, his right hand is powerful and he can put the punches together well. For my money, he will be the man to beat when the tournament begins, and I’m looking forward to it.”

Perdomo, a 33-year-old southpaw who lost to Germany’s Sartison in 2007 and to former Calzaghe victim Mario Veit in 2005, is no patsy but nothing in his record suggests that he will cause any more diversions for Kessler. The bravest of his ancestors were once buried on ships, which were set on fire and cast out to sea on this floating island of flames until the soul of the brave warrior rose slowly with the smoke. This Viking warrior has some rampaging on which to catch up.

Brian Doogan covers boxing for the Sunday Times of London