 Bosz would leave for Borussia Dortmund following the conclusion of the 2016–17 season and was replaced by Marcel Keizer, head coach of Jong Ajax and former Ajax player himself.Keizer was only a week into his tenure when tragedy struck the club and the world of football as a whole.On 8 July 2017, academy starlet Abdelhak Nouri collapsed on the pitch during a pre-season friendly against German side Werder Bremen, due to cardiac arrhythmia.