The Daily Mail reports that United scouts were impressed by St Juste as they were compiling a dossier on PSV Eindhoven.
St Juste impressed for Heerenveen in the 1-1 draw with PSV last month.
The 18-year-old only made his debut for Heerenveen at the beginning of the year.
The youngster can play as a centre back but can also operate as a defensive midfielder.
