The Scot was at the Estadio da Luz on Wednesday evening to cast his eye over Eliaquim Mangala, Jackson Martinez and Ezequiel Garay ahead of the summer shake-up at Old Trafford
Manchester United boss David Moyes flew to Lisbon on Wednesday to observe the Portuguese Classico between Benfica and Porto.
His attendance at the semi-final of the Taca de Portugal offered an opportunity to personally assess several players being monitored by the Red Devils' scouting department.
Porto's leading scorer Jackson Martinez, their France international centre back Eliquiam Mangala and Benfica central defender Ezequiel Garay have all been included on United's long list of potential reinforcements for next season.
All three featured in the second-leg tie, which Benfica won 3-1, as the Scot watched from an Estadio da Luz box.
Moyes has often laid the blame for United's underperformance in his first campaign as boss on the group of players he inherited from Sir Alex Ferguson.
Though his own future remains far from secure as the Old Trafford hierarchy assess alternative coaching options, he has been permitted to continue working on plans for an unprecedented overhaul of that squad.
In addition to January's club-record acquisition of Juan Mata from Chelsea, Moyes has proposed bringing in as many as six more players in the peak period of their careers – over the age of 25, with the quality and desire to accumulate trophies. His scouts have been looking for a striker and at least two new midfielders and defenders.
Martinez, Mangala and Garay are all expected to leave Portuguese football this summer as Porto and Benfica follow long-established strategies of raising revenue from their principal talents.
Moyes is well know for his diligence in watching potential signings in person before requesting a transfer spend from his employers.