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The 35-year-old American star axed Breland from his camp after the boxing trainer threw in the towel in Wilder's devastating defeat to Tyson Fury last February.
Breland, 57, recently criticised Wilder and branded him "untrainable" ahead of the Fury rematch, saying that a "coach can only teach someone if they're willing to learn."
Wilder, who hasn't fought since his defeat to Fury, launched a scathing attack on Breland and called him out by saying that he is 'envious' of him.
Now, Hearn has weighed in on Wilder's feud with his former co-trainer and questioned why the KO artist was talking about himself in the third person.
The 41-year-old Matchroom chief told iFL TV: "Go and listen to that interview from Deontay Wilder last night. He's completely lost his mind, completely lost his mind.
"When you start talking about yourself in the third person, 'Kings, let me tell you what kings do.'
"What are you talking about? Kings? 'Yeah, kings, because I'm a king.'
"You're not king. You got beat. You could become king, but you're not at the moment."
Wilder activated his rematch clause to face Fury for the third time, but the trilogy bout has been cast in doubt amid an ongoing legal situation.
Fury claimed that he has 'moved on' from facing the 'Bronze Bomber' as talks continue over a mega-unification clash with fellow Brit Anthony Joshua.
Wilder has since hurled unsubstantiated claims that the 'Gypsy King' 'cheated' in their second fight, along with sensational statements that he was spiked by his former trainer.
Hearn admitted that he wants to see Wilder return to the squared circle, but he hasn't ruled out the possibility that Martin could beat him.
"I really wanna see Wilder back, he's great for boxing, and so's Andy Ruiz," Joshua's promoter said.
"It's a good fight, Charles Martin can fight. I know 'AJ' cleaned him out in two rounds but that was a great performance.
"Charles Martin can fight. He was a good fighter then and he's a good fighter now.
"Charles Martin might beat Deontay Wilder."
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