The 18-year-old was named man of the match in Godenzonen's thumping 4-0 friendly win over Celtic on Saturday, putting in a fine display up front despite failing to get himself on the scoresheet.
His coach agreed that the Dane has the potential to become a top-class player, but insisted that he should be given the time he needs to develop.
"He may very well be [a great player]," he told Eredivisie live after the match. "He's pretty good, but still only a second-year player. He can also play in the youth team.
"He has the qualities to become a major player.
"There are of course no guarantees. He can have an injury or a fall. The scouts have a lot of insight and need to see that this is really him. If he develops, it would be stupid not to include him in the first-team squad.
"He will have to deal with media attention. We have to see if he's going to float or stay with both feet on the ground."
De Boer was pleased with his side’s performance against the Scottish champions, believing them to be on course for a good start to the season, even though they were unable to convert more than four of their many chances.
"We dominated the game,” he added. "We got 10 good chances, four of which were goals. Too bad we did not have the last extra push we could give, but I saw some nice attacks.
"We are on the right track. They played with the philosophy we like to see, especially in the [Amsterdam Arena]. The boys had the intention to implement what we want to see."