After finishing runners-up in both the Premier League and FA Cup, Jose Mourinho has set about trying to bolster his squad for an improved challenge next season.
Among United's targets is 19-year-old Porto full-back Dalot, who is preparing to switch the club he joined in 2008 for Old Trafford.
There is a good chance of a deal being reached between United and Mourinho's former club instead of using the 20 million euros (£17.5m) release clause that soon becomes active.
Dalot, a right-back capable playing on the left, has only made a handful of senior appearances for Porto, but is considered a huge talent and has attracted interest from many teams across Europe.
Long-time target Gareth Bale's clear agitation at Real Madrid will see his future monitored by United, while several players could exit this summer.
Speculation continues over the future of Daley Blind, Anthony Martial, Matteo Darmian and Luke Shaw, while divisive midfielder Marouane Fellaini's contract expires this summer.
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