Manchester United boss Jose Mourinho is believed to have ordered his spies to keep a closer watch on the Ajax academy graduate, who came to prominence last season and is firmly on Barcelona's radar.
Manchester City and Tottenham Hotspur both had £50m bids turned down this summer for the starlet, with his club insisting the classy 21-year-old isn't leaving the Amsterdam Arena anytime soon.
It's understood United are still on the lookout for another central defender and the fact De Jong is equally comfortable playing there or in central midfield, is something which is providing Mourinho and his backroom staff with some serious thought.
The Red Devils could hold an ace up their sleeve in former United goalkeeper Edwin van der Sar, who retains close links to his old club and is now the Chief Executive Officer at Ajax.
De Jong earned rave notices for his mature display in Holland's 2-1 to France in the Uefa Nations League and will no doubt have impressed the watching United representatives.