The Briton was outclassed by the Ukrainian at Tottenham Hotspur Stadium last weekend, dropping the IBF, WBO and WBA belts to scupper hopes of an undisputed title fight against the winner of Tyson Fury vs Deontay Wilder 3 on 9 October.
But Joshua, who has a rematch clause, insists he is in a good mood since reflecting on the second defeat of his professional career.
Joshua wrote on social media: “I’ve watched the fight, analysed my preparations & identified my mistakes. I’ve learnt my lesson.
“Thanks for sending love and checking in. Don’t worry about me. My spirit is strong!”
While Joshua’s promoter Eddie Hearn insisted his fighter “has got to make changes” for the rematch.
“Weirdly it’s a lot easier to take because you know how good Usyk is, and you always know if you don’t get it right there is a chance you can get beat,” Hearn said.
“The Ruiz fight, I guess we were probably a bit naive at the time, almost walking on air that AJ would steamroll through everyone and that was just one bolt from the blue that you sort of couldn’t get over for weeks. Tonight, you just say ‘it’s sport, you’ve got beaten by the better man, what are you gonna do about it?’
“(Joshua’s) mind is working overtime already, he’s a very deep thinker. He’ll beat himself up for a while...but he dedicates everything he does to the sport. So it’ll cut him deep, but the Ruiz fight, very different. Tonight he got beat by a pound-for-pound fantastic fighter.”
“He’s got to make changes, he’s got to get better. Usyk will probably — I’m pretty sure he’ll be the favourite going into the rematch.”
Speaking ahead of his fight with Wilder, Fury had some sage guidance for Joshua if he takes on former undisputed world cruiserweight champion Usyk again.
Fury said: “My advice to Joshua in the rematch is get stuck in the best way he knows how, put his best foot forward and swing away, Jack, swing away.
“Was I absolutely wounded that (Usyk) won? Yes I was. I was hoping Joshua could win the fight, but he couldn’t – and that’s none of my business.
“The only thing I’m bothered about is beating Deontay Wilder, and that’s the most dangerous heavyweight out there. In my opinion, Wilder beats Joshua, Usyk, all the rest of the division, comfortable – but he cannot beat me.”
Register for free to continue reading
Registration is a free and easy way to support our truly independent journalism
By registering, you will also enjoy limited access to Premium articles, exclusive newsletters, commenting, and virtual events with our leading journalists
Already have an account? sign in
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies