When Nathan Cleverly agreed to fight Sergey Kovalev on August 17, the Welshman would have been fully aware that he was taking on the biggest challenge of his 26-fight career.

Cleverly has defended his WBO light-heavyweight title on four occasions since he won the belt against Aleksy Kuziemski in May 2011, but he has yet to face a man with the power of the heavy-handed Russian.

That has ensured that this weekend's showdown in Cardiff will represent Cleverly's biggest opportunity to secure the unification fights that he has been craving for the best part of 12 months.

However, if the 26-year-old is dropped by the undefeated knockout expert, not only will it see the first blemish on Cleverly's record, it will also cast doubt on whether he can be classed in the same category as Bernard Hopkins and Chad Dawson.

What has brought Cleverly the success that he has already achieved is his ability to out-box whoever has been placed in front of him.

Tommy Karpency, Shawn Hawk and Robin Krasniqi did not possess the class to trouble Cleverly, but he was taken to the limit by Tony Bellew before securing the win by majority decision.

The Caerphilly-born fighter has developed a reputation of a quality operator inside the ring, but in truth, there is a possibility that it has been exaggerated due to the ability of his opponents.

Only on Saturday evening will we see the true capabilities of Cleverly, because Kovalev has proven himself to be a wrecking ball that has the potential to dominate the division.

He has blasted through his last four opponents in 10 rounds to secure his opportunity against Cleverly, and there is little doubt that the Welshman's chin is going to take a severe going over.

The big question is whether Cleverly can sustain the punishment for 12 rounds. He is the better boxer, but he is going to get drawn into a fight with Kovalev, and it's unknown whether he can cope with the powerful Russian.

The danger in this fight is that even if Cleverly does get the better of Kovalev for the opening stages, he is always going to be susceptible to one huge shot from the 30-year-old, and that can be enough to destroy the Welshman's dreams of an encounter with Hopkins.

Cleverly has longed for his opportunity to face the American legend, who is coming to the end of a distinguished career that has spanned a quarter of a century.

The IBF holder potentially has just two or three fights left in him, which places extra importance in the outcome of Saturday's bout.

At 26, defeat would not spell the end of Cleverly's career as a top-level fighter, but it would put paid to a Stateside date with Hopkins.

The desire for that match could have contrasting effects on Cleverly, because it could strengthen his focus against such a strong threat in Kovalev.

But if Cleverly already has eyes on Hopkins, it could see him head into Saturday at less than 100%, and if that's the case, Kovalev will become the new WBO light-heavyweight champion.