The 21-year-old is the subject of increasing interest from a number of sides around Europe, however the former England coach is not yet resigned to losing his star man
The 21-year-old was an unused member of Netherlands' squad at Euro 2012 and has been heavily linked with a move to the likes of Newcastle United and Borussia Monchengladbach.
The 51-year-old has stressed his hopes of holding onto the forward in the past and that it would take a sizable offer to convince the club to let the player go.
"De Jong would stay if it were up to me - unless stupid money is offered," he told De Telegraaf. "The club know what I think about it.
"I think it's best for the club and the player if he stays another season. I think he should have another year. Luuk has it all, but a transfer to a foreign club either succeeds or fails with maturity.
"Players have left too early in the past, such as Eljero Elia and Marko Arnautovic. So that's my advice to him."
Reports have suggested that Alan Pardew has offered 14.9 million euros for the promising attacker, and showed interest in the player in January before Papiss Cisse moved to the Sports Direct Arena from Freiburg.