Slager, 20, signed an 18-month deal with the Sky Blues in the January transfer window from Eredivisie outfit RKC Waalwijk.
He made one FA Cup start and three substitute appearances in League One for the midlands club.
Coventry manager Steven Pressley told the club's official website: "As we all know it is sometimes difficult for a player to adapt from one country to another and even experienced players have struggled in the past.
"It's regrettable that we find ourselves in this position as Denzel is a talented young player but at this moment in his development he would prefer to continue his career in his homeland.
"We completely appreciate the level of commitment Denzel has shown and we wish him all the very best in his future career."