He said: "There is interest from English clubs and clubs from the Eredivisie.
"However, Everton are the only club to contact me about Bob. It's not concrete yet, but they have scouted him regularly this season.
"Everton have been following Bob since the youth World Cup last summer.
"We'd like to keep Bob, but we are open to a transfer if Everton or another club are willing to pay a decent transfer fee."