Defending champion Thomas Pieters, a captain's pick in the European Ryder Cup team, has pulled out of the KLM Open after an adverse reaction to an insect bite.

The 24-year-old Belgian star was to have started the defense of his title Thursday at The Dutch course in Spijk, but organizers said he would not tee off. His withdrawal comes three weeks before the Ryder Cup starts at Hazeltine.

Pieters finished fourth at the Olympics and birdied the last three holes to win the Made in Denmark tournament last month, making him difficult for captain Darren Clarke to ignore as he pondered his wildcard choices. Pieters will be one of six Ryder Cup rookies on a European team seeking an unprecedented fourth straight victory in golf's prestigious team event.