Transfer speculation continues to mount as Diogo Costa has been linked in recent days with a move to Chelsea. The goalkeeper, currently playing for Porto, could add a new dimension to the squad if the rumoured interest turns into an official approach before the end of the transfer window. PSG, Aston Villa and Galatasaray have not withdrawn their interest and could still influence the outcome. With only 31 goals conceded in 27 (1.15 per game), Chelsea have been one of the stronger defences in the Premier League this season.. Diogo Costa would be asked to keep that standard and provide dependable cover when needed. Porto have also been linked with Ivan Jaime and Youssef Chermiti while Chelsea are reportedly monitoring Yasin Abbas Ayari, Iliman Ndiaye and Dani Olmo. Want more transfer rumours like this? Follow us on Twitter @PlayerSwitchCom for up-to-the-minute transfer news direct to your feed.