Manchester United had scouts posted at Vitória Guimaraes's 1-1 draw with Belenenses on the weekend.
Record says scouts from United, AS Monaco and Sevilla were in attendance.
United goalkeeper Joel Pereira is on a season-long loan with Belenenses, though was on the bench for the game.
Among the players on show was Vitoria midfielder Bernard Mensah, who counts on Jorge Mendes as his agent.