Last summer, it was Paul Pogba making a spectacular return to Manchester United. This summer, it could be Cristiano Ronaldo returning to Old Trafford.

With Ronaldo seemingly desperate to leave Real Madrid as soon as possible, there is talk of him rejoining United in a sensational move.

But what chance do the Premier League giants actually have of landing the Portuguese superstar?

Well, reports in the past few days have suggested United included a sell-on clause when they sold him in 2009. If that was the case, United would be entitled to a percentage of the selling fee.

For example, if the Red Devils included a 20% sell-on clause when they sold Ronaldo in 2009 and attempt to sign him for £150 million this summer, they will be entitled to £30 million - meaning the transfer would only cost £120.

United would have a far greater chance of securing a deal for Cristiano if they had including such a clause as they would be willing to spend that little bit extra.

However, there’s bad news.

United's big mistake

The Daily Mail are reporting that United failed to include a single clause in the deal in 2009.

At the time, the club insisted on the £80 million to be paid upfront, making it a world record fee, and not bothering with any possible clauses.

Oh, how they must regret that right now.

However, if Jose Mourinho and co. really want to sign Ronaldo, they won't care too much about how much they need to spend.

He may be 32, but he will no doubt pick up his fifth Ballon d'Or after he helping Real win La Liga and the Champions League last season. 

Ronaldo is reported to be keen on a return to Manchester. Whether the club can secure the deal remains to be seen.