Joshua defeated Joseph Parker on points in his first 12-round fight as a pro on March 31, but the former knockout king failed to spark against the New Zealander.
The 28-year-old won virtually every round against Parker, but his display was criticised by the likes of Tyson Fury, who claimed the unification fight was abysmal.
And Tyson seems to think Joshua’s performance fell flat and admitted he was not so convinced by AJ’s credentials.
“Joshua looked like he was the guy to (become undisputed champion) but in his last fight, he did not impress me,” Tyson told Showtime.
“(Deontay) Wilder is improving, he’s getting better.”
Joshua is now on the hunt to secure the final major world title, with WBC champion Deontay Wilder the only other remaining belt holder.