Matty Harris has shared the ring with Anthony Joshua and Daniel Dubois, but has no problem picking the winner.
Joshua and Dubois will meet in a huge heavyweight dust-up for the IBF world title on September 21 at Wembley Stadium.
Joshua will challenge Dubois for the IBF belt.
It is an intriguing affair, with AJ considered the narrow favourite over his domestic rival given his experience at the top level and ferocious punching power.
And British star Harris, who has shared sparring rounds with both, insists Joshua has the tools to stop the clash inside the distance.
“I think Joshua might have a little bit too much experience for Dubois,” he told Pro Boxing Fans.
“Dubois isn’t gonna walk him down the way he walked Hrgovic down. I know Hrgovic can punch, but his shots, a lot of them were fast and he looked off balance.
“Dubois will be a little bit more measured because he knows he can’t get hit that clean off of Joshua, but if he’s more measured that kind of plays into Joshua’s hands.
“Dubois, he’s got an impressive gas tank, what heavyweight do you know that throws over 50 punches a round?
“When he boxed Miller he consistently threw over 50 punches over ten rounds. It’s a lot of punches from a big man.
“I’m gonna just call it and say I think Joshua knocks him out. I don’t think Dubois has got a good enough defence, he’s pretty straightforward.
“I’ve made up my mind – I think Joshua knocks him spark out within eight rounds.”
Joshua has been in scintillating form since changing trainer to Ben Davison, rediscovering his power-hitting form with two stoppages over Otto Wallin and Francis Ngannou.
Harris has backed Joshua to get the job done emphatically.
He will have the added motivation of becoming a three-time champion, taking away the belt that Dubois was awarded following his win over Filip Hrgovic.
Dubois’ win over the Croatian was brutal and thrilling, but has raised question marks regarding his defence in the aftermath.
But his trainer Don Charles is adamant doubters will be proved wrong, as they work on their defence for the upcoming Joshua test.
“We have a lot of work to do,” he told talkSPORT.
“The defence, everyone has latched on to that and him getting with right hands. Yes we can see that and we are trying to improve.
“They say ‘he will get knocked out by AJ’ because he is leaking right hands. But in boxing when you throw a right hand, you are also in danger of being hit with one yourself.
“If they are foolish enough to bank on that, they have something else coming.
“We aren’t ignorant we are going to work on it. He took far too many against Hrgovic.
“That wasn’t the plan, but we will rectify that in the Joshua fight and we are not going to this time.”