So this is very important for him, Although he did get a new trainer, but still as the first round starts, it will be just him and Dillian Whyte. And it will be more mental for Joshua here than physical. He might be in the best shape of his life, but if his minds has started to doubt that he can win, then it won't help him here, IMHO.
It's all in the mind now for AJ if he see flashes of the Ruiz fight in his mind in this fight. And we will see how Derrick James can motivate him in this fight. As @inthelongrun, he is training with a lot of great boxers as well. So hopefully, he will be extra motivated to train very hard in the same gym, sweating it out with the likes of Ryan Garcia and Errol Spence Jr.
So it's a mental game going forward for AJ, he should go back to his old style. And not be hesitant and let his hands go if needed. Because after the his first lost to Ruiz Jr., for sure majority of us has notice that AJ doesn't want to pull the trigger, and unsure without to punch 1-2 or just go chase the opponent in the ring without throwing any power punch.