MANCHESTER, England -- Manchester United are closing in on Porto's Portugal Under-21 defender Diogo Dalot, sources have told ESPN FC.
Jose Mourinho is hopeful of concluding a deal for the full-back, who has started just five senior games for his club.
Sources have told ESPN FC United scouts watched the 19-year-old in Porto's 0-0 draw with Liverpool at Anfield in the Champions League in March.
He impressed enough for United to consider activating the teenager's €20 million buy-out clause.
Dalot, who has already turned down an approach from Valencia, can play at right-back and left-back and would offer cover for Antonio Valencia and Ashley Young on both sides of Mourinho's defence.
Young will turn 33 in July while Valencia, United's regular captain last season, will turn 33 in August.
Matteo Darmian is expected to join Juventus in a £10 million deal this summer and there are still doubts about Luke Shaw's long-term future.
Young and Valencia made 77 appearances between them last season but there are concerns about their workload as United prepare for another campaign in both the Premier League and Champions League.
Mourinho carefully managed Valencia last season and the former Wigan man rarely played two games a week.
Timothy Fosu-Mensah and Axel Tuanzebe are set to return from loan spells at Crystal Palace and Aston Villa, respectively, to add competition for places at the back.