Casey Stoner believes he pushed his body too hard in trying to overcome a mystery virus that has forced him to withdraw from the next three MotoGP races.
The 23-year-old will not ride his factory GP9 machine in Brno this weekend or the back-to-back races in Indianapolis and Misano as he tries to overcome a mystery illness that had dogged him since early June.
Stoner has been fighting a mystery virus since he vomited inside his helmet on his way to third place in the Catalunya GP.
In the four races after Catalunya, Stoner missed the podium three times as he was persistently struck by chronic fatigue.
He returned to Australia for the summer break following a disastrous 14th place finish in the British GP hoping further extensive medical checks would help him get a firm diagnosis on his problems.
The results of the tests have not been disclosed, but Stoner has made the shock decision to withdraw from the next three races, the 2007 world champion targeting a return to action in Estoril on October 4.
Stoner, who has won 18 races for Ducati including two in 2009, said: "After five extremely difficult races due to my health, I returned to Australia to visit the sports doctors who have looked after me for many years. We have taken the difficult decision not to contest the next three rounds of the championship, to allow my body time to recover from the recent stress.
"The doctors believe that during the Barcelona race I was suffering from a virus, and, that I subsequently pushed my body too hard, leading to problems that have caused my fatigue since then. The doctors are continuing with many tests to try to understand these problems and make sure it does not happen again. I have spoken with Ducati and thank them for their understanding at this time.
"I feel very sorry for the factory, my team, my sponsors and the fans and I am also disappointed because the bike in the last races has been very competitive. I will be doing everything possible to come back at full strength for Portugal."