The Amsterdam outfit's technical director Louis van Gaal took in NAC's weekend clash with RBC Roosendaal with the specific intention of running the rule over Diba.
The 20-year-old has caught the eye of Ajax's scouting network since breaking into NAC's team last season, and the Breda club know they face a tough task to keep the youngster at the club.
Diba shone against Ajax in the Amstel Cup meeting between the two sides recently and it would appear he impressed once again.
"Van Gaal, just like in our cup match against Ajax, has seen that Diba is a talent," said NAC coach Ton Lokhoff.
