The defender has one year left on his contract but has refused to pen a new deal with his current employers, meaning that Sporting are keen on sanctioning a sale now so as to avoid losing him on a free next summer.
That has alerted Southampton, who are said to have agreed a £3.5million deal with Sporting for their man and are very close to agreeing personal terms with him as well.
Premier League duo Everton and Stoke City had also been credited with holding an interest in the defender, who has been capped three times by Portugal, but it seems the Saints have stolen a march on their Premier League rivals to secure him ahead of the new season.
A move to England will bring an end to a life-long association with Sporting for the 23-year-old, with him having joined the club at the age of eight. His impending move will also increase speculation surrounding the future of Nathaniel Clyne, who has been linked with a move away from St Mary’s this summer – with the Express suggesting that Liverpool and Manchester United remain keen on securing his services.