Joshua triggered a rematch clause in his fight and the duo are set for a showdown said to be the 30-year-old pugilist's true test of championship.
'He's put absolutely everything into this camp and couldn't have tried any harder. It's not a guy asking for an easy warm-up fight. Time and time again, he has gone in at the deep end before his time, he's doing it again.
Joshua can regain his heavyweight world titles in a spectacular second fight with Ruiz Jr in Saudi Arabia next Saturday night, live at the box office of Sky Sports, and Whyte returns to action against Mariusz Wach on the card.
Briefly, Ruiz, who has it in his dancing fists and feet to assassinate the legacy of Joshua, is a extraordinarily assorted world champion.
'It's tough, though - it's a 50/50 fight.More news: S'pore-based cryptocurrency promoter arrested for helping N. Korea
"The only thing Ruiz has to do is do what he did last fight".
"I spoke to him (Joshua) a couple of days ago, he's in Saudi Arabia and very happy".
Frequently, world heavyweight champions - and Ruiz holds the World Boxing Affiliation, World Boxing Organisation and Worldwide Boxing Federation belts - have a bulging entourage of brokers and backroom workers, all having fun with a race on the gravy prepare.
'Work ethic can't be denied.
"I think AJ will stop him - maybe between rounds five and seven if he sticks to his game plan". I hope he wins.More news: Colts fall to Titans 31-17 after 4th quarter implosion
Joshua admitted he had been forced to make "a few changes in my lifestyle", but claimed he is now "shooting straight" towards the belts.
"He was giving me dietary and training advice and that is maybe what people are talking about now when they see a difference in my body".
'The motivation is forever within me. I know he'll try to do the same if I knock him down.
Kubrat Pulev, whose only defeat of his 29-fight career was against Joshua victim Wladimir Klitschko in 2014, is expected to fight the victor of the meeting dubbed the "Clash on the Dunes".More news: Inter leapfrogs Juventus to top Serie A as Bianconeri draw