The Manchester Evening News reports Mourinho shortlisted Dias among potential centre-back targets in the 2018 summer transfer window but United vetoed almost all of Mourinho's suggestions.
Mourinho had intimate knowledge of Portugal international Dias due to his contacts at Benfica and through his agent Jorge Mendes, who also represents Dias.
Dias was 21 at the time of United's interest and played against them twice in the 2017 Champions League group stage. Two club scouts watched Dias in April 2018 after United bought Victor Lindelof from Benfica in 2017, but the recruitment department was only receptive to signing a more proven centre half.
Dias, 24, was voted the Football Writers' Association Player of the Year on Thursday and is expected to claim the Professional Footballers' Association award.
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