The financial fettle of boxing has always depended on the ability of fighters such as Muhammad Ali and Oscar De La Hoya to attract crossover fans - the sports fan who may not be overly interested in boxing but who might buy one or two pay-per-view bouts a year.

The battle for the heavyweight crown has been the main draw for such fans. However, since Lennox Lewis retired in 2005, there has not been a sole, undisputed heavyweight champion.

At various times, there have been three or four titleholders, each wearing the crown of one or more of the different governing groups (WBC, WBO, WBA, IBF and now the fledgling IBO). In boxing circles, these governing bodies are affectionately known as alphabet soup.

Wladimir Klitschko holds the IBF, IBO and WBO belts. The Ukrainian, known as Dr Steelhammer owing to his PhD in sports science and his lethal right hand, is recognised as the best heavyweight in the world, with a record of 51 wins, including 45 knockouts, and three defeats.

Samuel Peter, a Nigerian, is the WBC titleholder. Klitschko and Peter tangled in 2005 before either of them held a belt. Klitschko, despite being knocked down three times, won on points.

Boxing buffs agree the winner of their rematch will be acknowledged as king of the heavyweight hill. However, before that bout can take place, 28-year-old Peter will have to ward off another Klitschko, Wladimir's big brother, Vitali. They meet tonight in Berlin.

Though Peter holds the WBC belt, Vitali Klitschko, 37, has the bizarre title of WBC world champion emeritus. In 2005 when recurrent back and knee injuries forced him to pull out of a number of title defences, Vitali retired from thering. At the time, he was WBC heavyweight champion and, since he had never lost as a title holder, the governing body agreed that, as champion emeritus, Vitali could return to the ring at his discretion and be guaranteed a title fight.

It is this kind of intrigue that gives boxing's reputation black eyes and a broken jaw. Nevertheless, while eyebrows could be raised about Peter being required to defend his crown against the popular Ukrainian, Saturday's matchup is a compelling one.

Peter, the son of a minister, is one of the most feared punchers in the division. He has a record of 30 wins, including 23 knockouts, and the loss to Wladimir is his only defeat. At just over 6ft, he is shorter than most elite heavyweights. He tends to come right at his foes, often without jabbing or moving his head. As a result, he is easy to hit but has a sturdy chin and "the Nigerian Nightmare", as he is known, makes his rivals pay for their aggression with furious hooks and right hands.

Peter, upset at having to make a mandatory defence against Vitali, has vowed to knock out both Klitschko brothers. Vitali has not fought since he defended his WBC title in 2004. In June 2003, he tussled with then champ Lennox Lewis, and gave him all that he could handlea good fight before Lewis opened a huge gash over Klitschko's eye, stopping the bout

Lewis told me: "Vitali is strong and tough. He has an awkward style and is hard to hit squarely. If I were Peter I would press him very hard, get him up against the ropes and test his bad back - which has been injured so often."

Emanuel Steward, who trained Lewis, Thomas Hearns and now works with Wladimir Klitschko, emphasised Vitali's awkward style and said: "If, after four years, Vitali is 100 per cent, he could give Peter a very hard time. He gives you a lot of different angles and, at 6ft 7in, is much taller than Peter. Vitali could keep him outside with his jab.

"But Peter is very powerful and again Vitali would have to be at his best and that is hard at 37 and after such a long layoff."

Vitali, who has won 35 of his 37 bouts, has never been knocked down and packs a potent right.

Prior to Vitali's retirement, the Klitschko brothers were engaged in the Orange revolution in Ukraine. Vitali is an official adviser to the country's president and is a member of the city parliament of Kiev.Even now as he prepares for a title fight, he will be on the phone discussing a proposed law one minute, pounding the punchbag the next. It is doubtful that there is a more politically active athlete in the world today. A fitness fanatic, Klitschko kept in trim during his hiatus by going to the boxing gym early every morning before heading to his government office.

Vitali has earned a lot of money and has interests outside sport. I pressed him about a comeback. He said: "A long time ago, Wladimir and I promised my mother we would never fight one another. It has been our goal for many years to share the heavyweight title. And this is our best chance to do this." But as many of the boxing cognoscenti have noted, what may be good for the brothers may not be good for the health of the fight game. With Wladimir holding two of the other belts, a Vitali victory would defer the hope of anointing a unified heavyweight champion.

Gordon Marino is a boxing trainer and philosophy professor at St Olaf College, Northfield, Minnesota