Lennox Lewis has encouraged Anthony Joshua to 'learn from this and improve' following Saturday night's defeat to Oleksandr Usyk.
The Brit was beaten by Usyk in a unanimous decision defeat at Tottenham Hotspur Stadium.
Joshua, 31, surrendered his WBA, WBO and IBF world title belts in London after a lacklustre performance.
Fighting out of Simferopol, Ukraine, Usyk (19-0, 13 KOs) boxed his way to a landslide unanimous decision win, and captured the belts with relative ease.
And according to Lewis, 'AJ' let himself down with the way he turned up to fight.
“Gotta [sic] give it up to Usyk on a great tactical performance tonight,” he wrote on Twitter.
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"“For Anthony Joshua it’s not the end of the road, but u [sic] can’t be so tentative or wait till the 8th round to turn it on.
"Learn from this and improve.”
“Usyk showed his pedigree in the ring tonight,” he tweeted.
“Amateur Champion. Olympic Gold medallist [sic].
“Undisputed Cruiserweight Champion and now World Heavyweight champion.
"It pays to take the long road, put in the hard work and aggressively go after your goals.”
"No comment", he replied when asked if Joshua needs to shake things up with his training setup.
Lewis had previously urged Joshua to axe his trainer Rob McCracken when he was shocked by Andy Ruiz Jr in June 2019.
Meanwhile, Matchroom promoter Eddie Hearn believes Joshua has a lot of work to do if he wants to win a rematch with Usyk next spring.
AJ has revealed plans to exercise an immediate rematch clause - which is being targeted for the first quarter of next year.
Speaking after the fight, a disappointed Hearn told BBC Sport: "He will have to make fundamental changes, he will have to box differently.
"I can't see AJ taking a 10-round fight, he boxes twice a year and maybe that is something we will have to look at.
"He is going to go away and all he will do is think about Oleksandr Usyk. He will be thinking: 'How can I beat him, how can I improve?' He is obsessed with improving.
"I just feel there is so much more to Anthony Joshua in that fight but he will have to do a lot more in the rematch to be victorious."
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