Tyson Fury's manager Frank Warren has questioned rival Anthony Joshua's ability to regain his place among the world's leading heavyweight boxers.
Warren urged the Londoner not to take a rematch with Andy Ruiz Jr, who defeated him in New York earlier this month as a late replacement following Jarrell Miller's positive drug test.
"I do have my doubts," Warren told BBC 5 Live's Sportsweek. "I don't think he should take the rematch. Maybe he should take some time out and regroup, I don't know.
"That's his decision. But he'll be fighting a guy who next time will have more than five weeks' notice and go into a proper training camp.
"I'm not going to say or make any predictions about the shape of his body, but he's got fast hands and I believe he's got Joshua's number.
"He's taken Joshua's best shot and he knows he has the punching power to do damage to Anthony Joshua."
Warren said he did not know who Fury will fight next, but that it would be someone "in the top five" - adding that he expects the British boxer to fight American Deontay Wilder early next year.
Fury said after his second-round stoppage of Germany's Tom Schwarz in Las Vegas on Saturday night that dates of September 21 or October 5 had been agreed in principle for his next bout.
"First of all we'll see who's available and we'll work on that over the next week and we'll make it happen," Warren said. "I genuinely do not have a name at the moment.
"It's highly probable that (Wilder v Fury) fight will happen early next year.
"I can't go into the details. I don't think the problem is the money, all parties want to make this fight happen."
Our heavyweight world rankings
1. Tyson Fury
If the 30-year-old was not already considered the very best when he returned from essentially three years' inactivity to outbox the dangerous Deontay Wilder in December's thrilling draw, when his performance deserved victory, then Anthony Joshua's defeat by Andy Ruiz Jr and the victory over Schwarz puts his status beyond doubt. At a time when the heavyweight division is again thriving, Fury is its most charismatic and talented fighter.
2. Deontay Wilder
The WBC champion, 33, is among the most powerful punchers in history, as he again demonstrated with his recent first-round stoppage of the tough Dominic Breazeale, but was fortunate to be awarded a draw when he defended his title against Fury. Before Joshua lost, Wilder would have been considered third.
3. Andy Ruiz Jr
The Mexican, 29, produced one of the greatest upsets in heavyweight history earlier this month when he recovered from a third-round knockdown to unexpectedly stop the previously-undefeated and highly-rated Joshua in seven. Ruiz Jr even accepted the fight at late notice; they are expected to have a rematch later this year.
4. Anthony Joshua
The decorated Olympic gold medallist should be in his prime but showed signs of regression throughout a poor performance as he suffered his first defeat against Ruiz Jr on his US debut. If he really is as good as he previously suggested and many continue to believe, he will convincingly avenge that defeat in an immediate rematch, and then pursue fights with Wilder and Fury.
5. Oleksandr Usyk
Ukraine's outstanding Usyk, 32, furthered his status as one of the greatest cruiserweights in history in his past fight, when he explosively stopped Tony Bellew to unify the IBF, WBA, WBO and WBC titles. He is yet to make his heavyweight debut but will do so later this year, and possesses such natural boxing abilities and athleticism that he already appears capable of immediately threatening the division's three biggest names.