That’s the belief of his heavyweight rival Tyson Fury.
Anthony Joshua will take on Ruiz in a rematch in December, after his shock defeat in June.
The British star lost his WBA, WBO and iBF world heavyweight titles to Ruiz in shock fashion in his American debut.
Joshua went into the fight with late replacement Ruiz as the heavy favourite with pundits and fans, but was defeated in stunning style.
The 29-year-old was knocked down three times before being stopped on his feet by the Mexican underdog.
He will have the chance to recapture his old belts on December 7 in Saudi Arabia, after the pair’s rematch was confirmed earlier this week.
But Fury believes that boxing fans have lost interest in Joshua after the defeat.
Speaking to TMZ Sports after confirming his heavyweight contest with Otto Wallin, Fury slammed ‘AJ’ and mocked him for losing to Ruiz.
“People aren’t interested in beaten fighters, as we saw with AJ,” Fury joked.
“AJ was like this great big man made out of marble, and then he gets knocked out by a little fat guy and everyone thinks ‘oh my god this ripped guy got knocked out by this little fat guy’.
“Now nobody likes him anymore, it’s like the bubble’s been burst.
“In boxing, once you’ve been pounded, nobody wants to know.
“Everybody loves a winner, and when you’re no longer a winner, you don’t get any more p***y.”
Fury will take on Wallin in Las Vegas on September 14 in his third straight bout in America.
The ‘Gypsy King’ will look to rematch Deontay Wilder early next year if he defeats Swedish Wallin.