By Frank Warren

When managing and promoting World class fighters, there comes a time when you have to roll the dice to determine whether they're exceptional or just simply very good.

That time has arrived for Nathan Cleverly this evening.  The Welsh light-heavyweight will enter the ring as a marginal underdog with the bookies for the first time when he makes a sixth defence of his WBO title against formidable Russian banger Sergey Kovalev at Cardiff's Motorpoint Arena. Both are unbeaten so, as they say in this trade, somebody's '0' has to go. BoxNation televise live.

It's not hard to see why the odds makers are sceptical regard­­­ing 'Clev's' chances of retaining.

Comrade Kovalev, aptly known as 'Krusher', has ko'd 19 of his 21 opponents, with 18 left seeing stars inside three rounds.

A product of the lauded Russian amateur system, he had well in excess of 200 unpaid fights, winning national titles and international singlets at both junior and senior level. He twice stuck gold at the World Military Games.

At 30, he lands in Wales in his physical prime and bursting with self-belief. Feted Florida coach John David Jackson – himself a former two-weight world champion and Don Turner, who masterminded much of Holyfield's career – have handled Kovalev's preparation and will front his corner this evening. US promotional giants Main Events and powerful American TV company HBO are also among the Russian's backers.

But, having turned professional at just 18, Nathan has served his apprenticeship. Having previously been Joe Calzaghe's chief sparring partner and capturing Commonwealth, British and European titles in record time, he has now reigned on the WBO throne for two and a half years.

Understandably, at 26, he now covets the mega paydays which can only come by snaring a TV deal with one of the major US cable networks. Despite our best efforts, unification spats with his rival 175lb world champions – most notably IBF king Bernard Hopkins – have proved infuriatingly elusive. Hence, Cleverly's decision to 'twist' against Kovalev.

It's a precarious situation and I admit that I will be a tad nervous sat at ringside tonight.  However in many instances in the past home grown favourites have defied popular opinion and triumphed in notably high risk fights. Styles, timing and home advantage are paramount.

In February 1995, Nigel Benn was deemed a complete 'no hoper' when I persuaded him to do his mandatory and put his WBC super-middleweight crown up for grabs against WBO counterpart Gerald McClellan, a truly savage puncher, at The London Arena.

That night the arena was a cauldron, even the press were standing on their seats. Nigel possibly should've been stopped after being clubbed clean out of the ring in the opening round. However, he dug as deep as any fighter ever has to triumph in round ten of what remains the most brutal, most tragic ring war I've witnessed.

Later that year, I won the purse bids for my man Steve Collins' rematch against Chris Eubank and put the show on in a stadium in Cork.  Collins had previously broken Eubank's unbeaten run on St Paddy's weekend, just a few months earlier but Eubank was convinced that Steve Collins' claims of hypnosis were the reasons for his first defeat.  But both myself and Steve knew that the real reason was that Eubank didn't fight three minutes of every round – he liked to strut and preen to disguise rest periods – whereas Collins had a prodigious work rate and knew that a repeat performance would inflict Eubank's second successive defeat in the Emerald Isle. The Celtic Warrior duly delivered in a magnificent contest in which both went toe to toe for the full twelve.

Frank Bruno had failed in three previous challenges for the world heavyweight title and Oliver McCall was fresh off a knockout win over Lennox Lewis and a victory over a faded Larry Holmes when I matched the pair at Wembley Stadium in September 1995.

I travelled to Vegas with big Frank and saw the 45 year old Holmes' jab give McCall problems just five months before. Like the Easton Assassin Frank also had an excellent left lead and was far fitter and fresher than Holmes. I gambled on big Frank bagging all the early rounds then holding off McCall – the toughest of cookies down the stretch, and that's exactly what happened.

Later that month, I took a risk by pitching Naseem Hamed against Cardiff's Steve Robinson, a terrific warrior, who had dispatched every quality Brit put before him.  That fight took place before 15,000 baying Welshmen at The Arms Park. It was the equivalent of taking him to Mexico and the crowd were hardly endearing to the Sheffield showman, who was spat at and had coins thrown at him!  Naz was just 21 and had never even fought up at featherweight but, as I sensed, he proved far too quick and won the WBO title with an eighth round stoppage.

Nine months later, for Naz's second defence in Newcastle, I accepted a voluntary defence against ex world junior champion Daniel Alicea. The Puerto Rican was unbeaten in 15 with 13 kayos and, at 23, was only going to improve by the time he reached the mandatory slot.  Sure enough, he wasn't ready and, despite getting dropped in the opener, Naz blasted him out in two; completely ruining him as a top class contender.  I became the first British promoter to promote at Madison Square Garden when Naz debuted in the US against local favourite Kevin Kelley. To say the fight was a barn stormer, is an understatement and Naz and Kelley unloaded bombs on each other in a real show of power, with both hitting the canvas before Naz prevailed and went onto become a World superstar.  It was certainly a risk worth taking!

Another time my man conceded home turf was when Danny Williams went to Louisville, Kentucky to front up to Iron Mike Tyson in July 2004.

The Brixton Bomber entered as a massive outsider and even US TV Executives were praying that Danny would get to hear just one of the 10 scheduled bells.   But again, I took a punt after being around Tyson in 2000 that he only had two good rounds in him and four more years of Tyson turbulent life had passed since then.  This was Tyson's first fight under a new trainer, Freddie Roach.  And I'm happy to say that I was right. Danny was plenty brave, absorbed an early shellacking, then detonated his own missiles to leave Mike ironed out in four.

My judgement proved sound when I managed to delay Ricky Hatton's mandatory challenge to favourite Kostya Tszyu by six months in June 2005.

The Russian was an absolute monster in his prime but was nearly 36 and had fought just once in 29 months by the time he finally stepped into the ring at a packed MEN Arena. All the stars were aligned and 'The Hitman' forced him to raise the white flag after 11 brutal rounds.

Nine months after at the same venue, Joe Calzaghe was similarly unfancied when Florida's unbeaten Jeff 'Left Hook' Lacy rumbled into town, boasting 17 kayos in 21 fights.   Calzaghe, cruelly dubbed 'Sicknote' by the Yanks, was on the brink of another withdrawal with nine days to go. However, after convincing him to fight, he delivered a quite majestic display to completely bamboozle the Yank. At his best, Joe was the best British fighter I've seen, bar none.

Cleverly's task this evening is as tough as any of the above but, I hope, my instincts will prove right again. But I have got it wrong on occasions!

Tonight's showdown will be broadcast live in Britain, across Europe and Russia and will also be shown on HBO in the US.  The eyes of the Media from both sides of the pond will be watching and passing judgement and I've invested heavily to secure home advantage for the Welshman. Now it's solely up to 'Clev' to deliver between the ropes.

He certainly can't indulge his lust for a tear up. It's imperative he maintains concentration, sticks to his far superior boxing skills, uses his height and reach, and dominates with straight shots and his phenomenal punch rate.  While it's certainly no formality, I'm quietly optimistic that he will.

After more than 30 years in the business, it's fights such as this that still give me a 'buzz' and I hope that this fight adds to the list of the great nights that I have mentioned.