Frazer Clarke lost to Joshua when they were novice amateurs on the way up and they have since sparred countless rounds at the English Institute of Sport in Sheffield.
Because of injuries, Clarke, silver medallist at the European Championship this summer, won’t spar Joshua in the countdown to the defence of his WBA Super and IBF belts against Kubrat Pulev at the Principality Stadium on Saturday, October 28.
But he’s watched Joshua sparring – and has been impressed.
Clarke watched him spar Martin Baklole Ilunga last week and said: “He looked more relaxed and fluent, not as stiff.
“The (Wladimir) Klitschko fight wasn’t just the best thing that happened to heavyweight boxing, it was the best thing that happened to Josh as well.
“He’s woken up.
“He was shocking in that fight, absolutely terrible, and he admits it. From what I’ve seen of his last few spars, he’s thinking more now. Before he was relying on brute strength a bit too much and now he’s thinking about what he’s going to do.”
Clarke insists Joshua isn’t just a puncher.
“He is good at everything,” said the 26 year old from Burton.
“He won the Olympics and you have to be a good boxer to do that.
“From what I’ve seen, he’s gone back to his boxing. He hasn’t shown the full range of his skills in the ring yet. But he shows it in the gym.”
Clarke has taken over as Britain’s top amateur super heavyweight after Joe Joyce turned over.
He should be fit for next year’s Commonwealth Games next April – Clarke will start as the favourite – and his ultimate target is the 2020 Olympics in Tokyo.
“That’ something I really want,” said Clarke.
“By the time I reach Tokyo I will have had another three years of sparring with AJ and I will be ready