William Carvalho
Carvalho scouted by both Arsenal and United. (Reuters)Reuters

Barcelona and Real Madrid have reportedly joined the race to sign Sporting Lisbon midfielder William Carvalho, who has also caught the eye of Arsenal and Manchester United.

The 21-year-old Portuguese international has impressed a number of European sides during the first half of this campaign, as has been named the best player in the Primera Liga by the supporters during October and November.

Juventus, Arsenal and United are monitoring the player and Spanish Newspaper Mundo Deportivo report that Barcelona and Real Madrid are also interested in acquire his services as they consider him as one of the best young talents in Europe.

Nevertheless, Sporting president Bruno Carvalho suggested recently that they are not willing to negotiate a deal which falls beneath his £37m release clause as they want to keep him in the squad.

"We are not interesting in his selling", he said.

With such a huge buy-out clause recent reports suggest that United were leading the race to sign Carvalho, by offering Nani as part of the deal as the Portuguese side are keen to be reunited with the winger.

At the same time, reports claimed that Arsenal scout Francis Cagigao was in Portugal scouting the player recently as manager Arsene Wenger is looking to add a young midfielder to the squad as as a long term successor for Mikel Arteta, who is nearing his mid-thirties.

Sporting sent Carvalho on loan during the last two seasons to continue his progress and this year he has shown that is ready to compete in the top flight with 15 domestic league impressive appearances.

Indeed, he has already been capped once by Portugal and he may have the chance to play in the next summer's World Cup.