Heavyweight also opened up on sparring between AJ and Dubois

DANIEL DUBOIS left Frazer Clarke on his backside and stunned in sparring – in what will be a stern warning to Anthony Joshua.

Joshua is expected to face Dubois in a Wembley homecoming bout in September.

Anthony Joshua with Frazer Clarke and Daniel Dubois

But it will not be the first time they have shared the ring following dozens of sparring rounds in Team GB’s Sheffield HQ.

Also involved in those sessions was unbeaten Clarke – who admitted Dubois even dropped him.

He told SecondsOut: “I have no shame in saying it, Daniel Dubois put me on my a**e with a left hook years ago. And he was young.

“I thought, ‘Oh my God, this f***ing kid is something else.’ Obviously, got back up and carried on sparring it happens in our division.

“But yeah, I’ve been on the side of the ring where these two have really had good exchanges and stuff.”

Rumours circled for years that a teenage Dubois also floored AJ.

Clarke remained tight lip of the speculation but backed Joshua as a favourite in the bout despite Dubois’ big win over Filip Hrgovic.

He said: “Anthony was always that little further ahead but yeah, father time happen and Daniel has matured and grown as a fighter and it makes the fight intriguing.

“I still have AJ as a favourite just because of the experience and I feel like if Daniel took the same 30 shots off AJ as he did off Hrgovic we’d be having a different conversation right now.

“He’ll have to tighten up in his defences but him and the team are not naive they’ll know that but he’s shown a different side to him. I look forward to it.”

Clarke, 32, is coming off a fight of the year contender against British champion Fabio Wardley, 29, which ended a draw with rematch talks underway.

Meanwhile, Dubois, 26, stopped Hrgovic, 32, in Saudi Arabia to claim the IBF “interim” belt.

Oleksandr Usyk, 37, stills holds the full world title after victory over Tyson Fury, 35, in their undisputed decider in May.

But due to their pencilled in rematch in December 21, he could be stripped of the IBF belt due to being unable to fight challenger Dubois.

So promoters hope Joshua, 34, can face Dubois for the title at Wembley.