World 100m and 200m record holder Usain Bolt will not run again this season due to a back injury.
The 23-year-old Jamaican was recently between by American Tyson Gay in a Diamond League meeting in Stockholm and will now concentrate on being fully fit for next year.
A statement from Bolt confirmed: "2011 and 2012 are very important championship years and I hope to be back fully fit and healthy.
"I am very disappointed to miss two of the top meetings (Zurich and Brussels) on the circuit, but trust that it is better for me not to take any risks this year.
"I would like to thank everyone for their support and look forward to coming back stronger next year."
Meanwhile, former 400m world champion Antonio Pettigrew has died at the age of 42.
Pettigrew won his world title in 1991, but later on in his career admitted to taking performance-enhancing drugs.