After visiting the canvas four times inside seven rounds, a dream American debut at Madison Square Garden unravelling into an unforeseeable nightmare, the former IBF, WBA and WBO world heavyweight champion emerged for a delayed post-fight news conference with a smile and good manners.
"I've dealt with some real big losses in life and bounced back. I feel like this is just part of a journey that I'm on," he said, having warmly embraced Ruiz in the ring afterwards.
"This is boxing. What I have to do is re-evaluate the situation, make it better and go again. We didn't come this far to stop, to fold under pressure. We came this far and I feel we can definitely go a lot further."
Unlike what unfolded for most of a stunning main event, it was classic Joshua. Talk of the "journey", of boxing's inextricable link to redemption stories. When the dust settles and the senses are unscrambled, it would be surprising if the 29-year-old remains so philosophically on-message.
Your favourite fighters and motivational posters will tell you setbacks pave the way for comebacks. That might sometimes be true, but it is rarely the case of setbacks like the one Joshua suffered against Ruiz.
This is Andy’s night, congratulations Champ pic.twitter.com/5gE8uFx4MG
— Anthony Joshua (@anthonyfjoshua) June 2, 2019
History tells us the 2012 Olympic champion's career is now heading in a different direction to the one that signposted undisputed dominance.
Ruiz's victory is heavyweight boxing's biggest upset since James 'Buster' Douglas dethroned Mike Tyson in Tokyo in 1990. Like the then-undefeated Tyson, Joshua has been robbed of his fear factor.
Vulnerability being laid bare in public – Joshua's up-and-down thriller against Wladimir Klitschko two years ago means this type of defeat felt possible, if not against Ruiz – is not an insurmountable problem.
Fellow Briton Lennox Lewis was sensationally stopped by both Oliver McCall and Hasim Rahman, responding to avenge those losses and regain his titles.
Joshua is likely to have the same chance in a rematch against Ruiz in the UK before the end of this year, but the manner of his loss is more troubling than when Lewis was dethroned.
McCall and Rahman both landed booming shots to earn stoppage wins. Such losses damage both ego and reputation but can be shrugged off in a way Joshua's collapse cannot.
After being dropped by a fierce left hook, Ruiz arguably threw his own lucky shot when he caught Joshua on the temple, robbing him of his equilibrium and planting seeds of doubt to shackle him the next time he goes for the big finishes that were the foundation of a sparkling career.
— Anthony Joshua (@anthonyfjoshua) June 2, 2019
While Klitschko let his moment pass at Wembley, Ruiz boxed with both skill and intelligence to take the beleaguered champion apart.
He launched calculated body attacks to sap his wounded foe. After his trips to the floor in the seventh, Joshua stood propped up in his corner with nothing left.
That meant the defeat had more in common with Tyson's against Douglas, a reverse where rivals can take note of the path laid out by an unfancied outsider.
WBC king Deontay Wilder undoubtedly enjoyed witnessing Joshua's questionable punch resistance, Tyson Fury will have observed his struggles with Ruiz's deceptively fast hands and Dillian Whyte will wonder why he did not bring his "Body Snatcher" nickname to bear when he was knocked out by Joshua in 2015.
All should rue not putting themselves in the position to snaffle the division's most valuable "0" as the affable Ruiz - a late replacement for Jarrell Miller - did.
Tyson's Tokyo torment came as his private life descended into a bleak soap opera, while Lewis fought Rahman at altitude with a woeful lack of preparation.
Excuses may emerge over the coming days and weeks, but Joshua was in fine condition and the star of his own lucrative show as it hit boxing's money market. The lack of mitigating circumstances is another damning element.
Despite everything, Joshua will enter any rematch as favourite, probably at a packed football stadium in the sort of mega event he incredibly made a staple of the sport in his homeland.
Mandatory obligations mean Ruiz is likely to have to relinquish portions of his crown to face Joshua again, meaning the path to an undisputed champion - and the window of clarity that would give to the division - has probably closed for this generation.
When it happens, that outing will feel so different to previous nights of delirium at Wembley and the Principality Stadium, where everything felt possible for a genuine superstar. Ruiz took that aura from Joshua and, unlike alphabet belts, you never get that back.
Photo Getty Images. Caption: Anthony Joshua is stopped at Madison Square Garden