Mexican-American Ruiz produced one of boxing's biggest upsets when he dethroned the previously undefeated world champion Joshua with a seventh-round stoppage at New York's Madison Square Garden.
Anthony Joshua says he chose to "reinvent" himself after defeat by Andy Ruiz Jr and feels "different" going into Sunday's rematch.
Anthony Joshua appears to be ready to conquer the world of boxing again after the British-Nigerian born pugilist shows off unbelievable body transformation ahead of his fight with Andy Ruiz.
"We've got to see where he's at because all the pressure is on him". The pressure isn't on me because I followed my dream, made my dreams come true.
Ruiz Jr said: "One punch can change the fight", said Ruiz Jr, ahead of the clash.
Whyte said Sky sports: "It's heavyweight boxing, what can I say?" Sometimes fighters lose, it makes them weaker.
"I know exactly what it's like when you have a lot of muscle, you want to stand there and trade but I don't think that's his style".
He had earlier defended his slimmer look in September saying he is focused on "sharpening the tools that I left out of the box".
Ruiz Jr shocked the boxing world with his win but Joshua exercised his contractual right to a rematch nearly immediately and just weeks later, the sequel was confirmed to take place in Diriyah, a small town on the outskirts of Saudi's capital Riyadh.
When asked if a rematch of Joshua can occur, Whyte said: "I hope so".
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.
"Win, lose or draw he has a future", Hearn told Sky Sports. "Even if he loses his next 10 fights, I would still like to rematch him".