Carvalho, 22, impressed for both Sporting Lisbon last season and with Portugal at the World Cup, establishing himself as one of the top young holding midfielders in Europe over the course of the last 12 months.
The Angolan-born midfielder's displays have attracted interest from some of the world's top clubs, with Arsenal and Manchester United both strongly pursuing Carvalho. United had been linked with a £37m bid - the value in Carvalho's release clause - as new manager Louis van Gaal looks to improve his midfield Carvalho would be the perfect complement to new signing Ander Herrera in midfield, offering the power and defensive ability to protect a fragile United defence.
Meanwhile, Arsenal reportedly had a £24m bid rejected for Carvalho recently, with manager Arsene Wenger desperately seeking to sign a holding midfielder who can also play at centre back - criteria which Carvalho fits into perfectly.
Most of the speculation to date has been surrounding Arsenal's bid to hijack United's interest, and then conversely United rekindling their interest in Carvalho as their bid to sign Juventus midfielder Arturo Vidal continues to stall.
However, there could be another twist in the plot after it was revealed that Chelsea sent scouts to watch Carvalho in action as Sporting Lisbon took on Academica as the Portuguese league season got underway. Lists of clubs that attend matches to watch players are regularly published in Portugal, and the list from the game between Academica and Sporting showed that Chelsea attended - and O Jogo believe that the Blues were watching Carvalho.
Despite landing Cesc Fabregas, Chelsea manager Jose Mourinho continues to be linked with moves for more midfielders - particularly defensive ones. With the transfer deadline approaching, Chelsea could now look to steal a march on their Premier League rivals with a big bid for Carvalho - although the midfielder was red carded in the game for two bookable offences, which may leave Arsenal and United still leading the race.
Mourinho is no stranger to some physical, aggressive play in his team, and surely they would base their assessment of Carvalho on more than one game.