The Denmark international midfielder is highly rated at the Amsterdam based club and with United preparing to take them on in the Europa League this week, Fergie is reportedly going to keep a close eye on the player.
A number of clubs have already expressed an interest in the 18 year old, including Real Madrid.
"There's been a lot of attention on him," Ferguson said. "Everybody's been watching him. We'll see what he's like."
Rumour has it that United are expected to purchase a new midfielder in the summer transfer window.