Manchester United have asked about Benfica's German-born Greece international goalkeeper Odysseas Vlachodimos, 29.
United want back-up goalkeepers after Crystal Palace opened talks over a deal for Dean Henderson, who also has an offer from Nottingham Forest.
Vlachodimos has made 225 appearances for Benfica since joining the Portuguese giants from Panathinaikos in 2018.
He played 34 games in the Portuguese top flight last season as Benfica claimed the title.
Man United are seeking cover for Andre Onana, after selling Nathan Bishop to Sunderland and Matej Kovar to Bayer Leverkusen.