Who did Diederik Boer replace to be behind a Dutch professional footballer?
Diederik Boer:  On 31 August 2014 Boer signed a three-year contract with Ajax to replace the departed Kenneth Vermeer as second keeper behind Jasper Cillessen. Jasper Cillessen: Jacobus Antonius Peter "Jasper" Cillessen (] ; born 22 April 1989) is a Dutch professional footballer who plays as a goalkeeper for Spanish club FC Barcelona and the Netherlands national team.
i don't know