Cristiano Ronaldo's price could come down if he has expressed a desire to leave, according to a football marketing expert

Manchester United are the only obvious club that could afford Cristiano Ronaldo, according to a football marketing expert.

The Real Madrid forward wants to leave Spain and is interested in the possibility of a return to United, according to Sky sources, who sold him in the summer of 2009 for £80m.

While Ronaldo tops the wishlist in the Chinese Super League, which saw its transfer window open on Monday, football marketing expert Esteve Calzada explained why United - who topped Forbes' Most Valuable Soccer Teams List this month - are the most likely destination for the player.

"If there is a team that can finance it of course it is Manchester United," Calzada told Sky Sports News HQ. "Even though he would make more of an impact at other teams that don't have such an impressive commercial appeal.

"Manchester United will save the big salary of [Zlatan] Ibrahimovic, they are back in the Champions League and receive the financial benefits of that. Definitely United will be in a position to afford this deal.

"The fact that he [Ronaldo] wants to leave the club can help drive the price down.

How does the Chinese transfer tax work? Any Chinese club wanting to sign Ronaldo, for say £200m, would also have to pay £200m into a national fund to develop young Chinese players, bringing the total cost of the transfer to £400m - before wages are taken into account.

"Even China is becoming more difficult because of the new tax, which means any transfer fee that is agreed, you have to pay the same amount in tax.

"When you come to Europe there are very few clubs that could afford him. Real Madrid is one, and United, then Paris Saint-Germain, Bayern [Munich] and Juventus, but those teams would probably have to sell players.

Paul Pogba's return to Manchester United was the only reason Juventus could afford Gonzalo Higuain, says Esteve Calzada

"Juventus were able to spend a lot of money on [Gonzalo] Higuain but just because they sold [Paul] Pogba to United."

Florentino Perez has been re-elected as Real Madrid president until 2021, and while Ronaldo's potential departure will be top of his agenda, history suggests a 'Galactico' signing is likely to follow.

Ronaldo's departure could be the perfect excuse for Real Madrid to sign Kylian Mbappe, says Calzada

The 70-year-old had made a marquee signing in every one of his four election years, and Calzada suggested selling Ronaldo could actually be part of a plan to bring in a new Bernabeu star to appease Real Madrid's supporters.

"Ronaldo is 32, maybe it's the perfect excuse to finance [Kylian] Mbappe, for example," Calzada added. "He [Perez] could be able to explain it to the public.

"Ronaldo has always been sad by the fact that he does not feel much love from the fans. If there is a time or an opportunity, it is probably now."