The 14-year-old gelding, with whom Michael won individual gold at the 2010 eventing World Championships, the 2011 European Championships and the 2012 Olympics,has an inflammation in a front hoof.
Sam was reported to be sound in training Bonn Rodderberg yesterday (20 August ) but showed signs of lameness this morning.
“It would have been really nice to restart with Sam after 2010 at the World Championships,” Michael said.
“Fortunately, it is nothing serious, but the World Championships has gone.”
Michael will still compete at WEG but will ride FischerRocana FST. The nine-year-old mare finished second at Luhmühlen this year.