By Wayne Veysey

West Ham are in advanced talks to sign Boavista centre-back Goncalo Cardoso for a fee of £3million, Football Insider has learned.

The Portugal Under-21 international is set to fly to London today to undergo a Hammers medical and put the finishing touches to a deal that will make him the club’s fifth summer signing.

A West Ham source has told Football Insider that an agreement has been reached between the two clubs after Portugese outfit Boavista accepted the club’s bid.

The defender, 18, has been granted permission to head to England and finalise the terms of a contract with the Premier League club.

There are not expected to be any issues with the rising star agreeing personal terms as he prepares to become West Ham’s fifth summer signing.

Cardoso made his senior debut for Boavista in October of last year and went on to make 18 appearances for the team, with 15 of them coming in league matches.

He has caught the eye of West Ham scouts with his performances at Portugal Under-19 level, where he has been capped 11 times already.

Cardoso is set to challenge for the centre-back role this season in Manuel Pellegrini’s side along with first-choice pair Issa Diop and Fabian Balbuena, as well as deputies Winston Reid and Angelo Ogbonna.

West Ham have already signed centre-forward Sebastien Haller, attacking midfielder Pablo Fornals and goalkeepers Roberto and David Martin this summer.

In other West Ham news, it can be REVEALED that the club are sweating over the fitness of four senior stars ahead of their Premier League opener.