The 17-year-old midfielder was watched by United scouts while scoring for Portugal under-19s against Spain this week.

Quina spent three years in the Chelsea academy after moving from Benfica. But he was released last summer and picked up by the Hammers.

Arsenal and Paris Saint-Germain are also keeping a close eye on the highly-rated midfielder, who has four senior appearances to his name.

David Moyes’ arrival at the London Stadium has “raised concerns” over his future in east London.

It is thought there may be a lack of first team opportunities as Moyes tries to steady the ship after replacing Slaven Bilic, according to ESPN.

Quina’s contract with West Ham runs until 2019 and a number of Europe’s elite clubs are said to be monitoring the situation.

If the Guinea-Bissau-born playmaker was to move to a Champions league side, Chelsea will regret losing yet another top talent at such a young age.

The Blues made the same mistake when they released Eddie Nketiah, who scored a brace on his Arsenal debut.

Quina made his maiden West Ham appearance when replacing Michael Antonio against NK Domzale in the Europa League in 2016.

He has also made two late substitute appearances in the EFL Cup this season.