The 22-year-old Portugal international has been a target for several Premier League clubs, including United, Liverpool, Chelsea and Arsenal. He was one of the best players in the Portuguese top flight last season, earning a call up to the national team for the World Cup.
He didn't figure too prominently in Brazil but is regarded to be the future of the Portugal midfield. Sporting have recognised his potential value, and have moved to snap up his remaining ownership rights.
They are now 100 per cent stakeholders in Carvalho, which is great news for United, Chelsea, Arsenal and Liverpool. Under Premier League rules, clubs cannot sign players who are owned by third parties.
But now Sporting have purchased his full rights, the likes of United and Liverpool are free to bid and Sporting will receive his full transfer fee.
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That has sparked speculation in the Daily Star that he could be put up for sale as early as January as the Portuguese giants look to cash in on their most promising asset.
It has long been reported that Carvalho has a £37m release clause in his contract, which means Sporting are in an extremely strong negotiating position. It's unlikely they would get near that amount, but it's a useful ceiling for a club famous for selling on top youngsters for big money.
Premier League ambitions
Speaking to the Portuguese Association magazine earlier this season, Carvalho revealed that he would like to test himself in the Premier League or La Liga at some point in his career.
"We all have ambitions and I hope to one day play in the best leagues in the world," Carvalho said. "The English or Spanish.
"It was not this year, but if I continue to do my job as I have done so, it will certainly come sooner or later."