Ajax coach Ronald De Boer has told want-away defender Jan Vertonghen not to sell himself short.

The Belgium is ready to quit the Eredivisie this summer and has Newcastle United, Arsenal, Tottenham and Liverpool among clubs chasing his signature.

"Look at Thomas Vermaelen , everyone saw him in his time as an Ajax player, now he is seen in England as one of the best defenders in the Premier League," De Boer said.

"And Vertonghen is better than Vermaelen.

"He has the potential to be as good as Jaap Stam ever was."