Tyson Fury believes Anthony Joshua is "finished" as a top-level boxer.
Joshua was beaten by Andy Ruiz Jr earlier this month in one of the biggest shocks in boxing history.
And as he prepares to take on Tom Schwarz in Las Vegas on Saturday, Fury delivered a damning verdict on his rival.
"When a man doesn't want to be there once, he will always do it and it's hard to come back from," he told the BBC .
"He did it that night and I don't think he will come back from it. Finished. Ask any top trainer who has been around the sport a lifetime. When he got to the ring I saw he didn't want to be there.
"Everybody thought that man could beat me. In what world could he ever beat me? What were people seeing? I don't know what people were looking at as I don't know what world he could have beat me."
Ruiz Jr's podgy physique was a stark contrast to Joshua's muscular frame - but it counted for nothing in New York.
And Fury added: "Physically Joshua could out-train everyone.
"He would break every heart monitor, has probably worn out every treadmill in the gym, smashes the bag, it's all very unimportant.
"Boxing isn't rocket science and today people are trying to make it a scientist thing. If you can fight you can fight if you can't you can forget about it.
"You can eat every protein bar in the world, when you get banged on the chin and panic, it don't really help you much.
"People who don't understand boxing look at a fight man and think he can't fight. The best feeling I got from it was the two best conditioned fighters in the last 20 years have been [Wladimir] Klitschko and Joshua and they both got done by two fat men."
