The 24-year-old striker suffered a right knee injury against Heerenveen and tests have revealed he has ruptured a ligament in the joint.
Utrecht coach Foeke Booy has revealed de Groot will be absent for a number of months and will struggle to return for pre-season.
The club are on the fringes of the European places in De Eredivisie and are into the final of the Amstel Cup, where they will face Twente on May 23.
