The British boxing hero suffered a second consecutive loss to the undefeated Ukrainian at the Jeddah Superdome in Saudi Arabia on August 20.
Joshua, 32, moved his training camp to Loughborough University after parting ways with longtime trainer Rob McCracken.
And coach Garcia, who worked alongside Angel Fernandes as part of Joshua’s corner for his rematch against Usyk, has said he must leave the UK to train with him in the US if they are to continue working together.
The 47-year-old told IZQUIERDAZO: “I told Anthony and all his team that, for me, the best way to keep working together is if Anthony comes to train in my gym in California eight weeks before a fight.
“From six to eight weeks, that’s all I need for a good camp.
“I told Anthony, ‘I need you to be around more fighters, more champions. I want you to have more fighters for competition, even if they are from the same gym, but you have to compete.’
“I told him, ‘You have to want to be better than them, and they will want to be better than you. It will work for all of you.’
“That is what is missing in his gym, the fighters to be competing against each other, where they don’t want the other fighter to do more than you.
“He needs a place with other world champions around.
“Anthony has always been alone in his camps, he didn’t have other fighters to train with.
“He needs to be in a cheerful environment, to interact with other fighters, other sparring partners.
“I think that that would help him a lot.
“I am a boxing man, and I told them that I know that he needs to be in a challenging gym.
“The other fighters will push him to do more and more. That helps a lot.
“Everyone else in the team is willing to train in California.
“I had a very nice conversation with them before leaving, and everyone agrees that this is what he needs.
“They said that they will talk to Anthony, and that they will need to convince him this is the best for him.
“In the end, he can decide differently, but his team accepted that the best option is to leave the UK and come to California for his training camp.”
Former world champion Garcia also believes Joshua needs to be pushed to the best of his abilities.
He added: “It will help him a lot to compete with other fighters in my gym.
“And mentally, he will not tell himself that he did enough work, that he is done.
“No, the other fighters will tell him that he still needs to do more.
“Those four months that I was in England with him were hard for me.
“Fortunately, I didn’t have a big fight with my other fighters. Jesse Rodriguez fought in June. And I travelled from there to England.
“I find it difficult for that to happen again.
“If they ask me to go back to England, it would have to be a special situation.
“If Anthony’s next fight is in early December, I would be available, because I don’t have big fights.
“But if Jesse Rodriguez or Jose Ramirez have an important fight, I would rather stay with them, and not leave.
“That is why I asked Anthony’s team to come to California, and they liked the idea.
“Now, they need to talk to Anthony and convince him.”