Manchester United reportedly scouted Porto defender Eder Militao during his team's 3-1 win over Nacional in the Primeira Liga on Monday night.
Militao, who started his professional career with Sao Paulo before moving to Porto in August 2018, has been linked with a number of European clubs in recent weeks.
United were recently credited with an interest in the 20-year-old, while Real Madrid have reportedly been scouting the Brazilian in recent weeks.
According to O Jogo, United sent one of their scouts to watch Militao in action on Monday evening and a favourable report was returned as the South American impressed in his team's victory.
Liverpool have also reportedly joined the race for Militao, who is said to have a £45m release clause in his Porto contract.