Anthony Joshua must be wary of Alexander Povetkin says Eddie Hearn

Joshua, the WBA, WBO and IBF world heavyweight champion, faces 39-year-old Russian Povetkin, who has only been beaten once in his 35-fight career - by Wladimir Klitschko in 2013.

“It’s a massive show, a massive event with the biggest star in world boxing and the best heavyweight in the world,” Hearn told Press Association Sport.

“But I’m a bit nervous because I think this is a much tougher fight than people give it credit for. Boxing fans know how big a fight this is and how tough a fight this is.

“Outside of Klitschko I think on paper this is the toughest fight of Joshua’s career so far.

“He’s expected to win. But Povetkin punches very hard, he’s got a good chin, he’s durable. I expect this to be a real test.”

Assuming Joshua comes through unscathed all eyes will be on a potential bout to unify the division against WBC title holder Deontay Wilder.

But Hearn has warned Wilder, who is due to fight Joshua’s fellow Brit Tyson Fury later this year, and his team to come back to the table or risk missing the boat.

“We want the undisputed fight, but it’s very difficult to make a fight when other teams aren’t particularly interested in talking to you,” added Hearn.

“For us it’s all about Saturday, then a WBO mandatory defence, but an undisputed fight would be allowed, it’s just a case of when we can get that done.

“My advice to Wilder’s team, if we beat Povetkin, is hurry up, because you haven’t got long.”