The manager of the Dutch national team, Ronald Koeman, has tipped the young Ajax centre-back to soon take the next step in his career.
Virgil van Dijk was sent back to Liverpool after the Netherlands' 3-0 victory over Germany at the weekend.
Virgil van Dijk almost cost Liverpool against Manchester City on Sunday.
Tottenham Hotspur are reportedly keen on Frenkie de Jong.
The Senegal forward scored eight Premier League goals for Everton this season.
Coaches like Eddie Howe might sound better but it is no surprise that Big Sam was the man for Everton this season.
Ronald Koeman has backed Ajax's Hakim Ziyech to join Everton.
Klaassen has flopped at Everton since in his move from Ajax last summer.
Everton recently put out a survey asking season ticket holders and club members to rate manager Sam Allardyce.
Former Everton striker Tim Cahill recently claimed the club have lost their identity.