The ace South African athlete's withdrawal from the Oct 3-14 event was announced by Athletics South Africa citing that Semenya could risk a major injury if she travelled to Delhi.
“Caster has been experiencing back pain for some period of time and continued to have pain after competing in a cross-country event at the weekend," South Africa"s Commonwealth Games chief Tubby Reddy said.
“Our doctor has since examined her and ... (the) scan confirmed that she most certainly has a back problem. We are satisfied that this is a bona fide injury and as such, SASOC and Athletics South Africa agree that we are not in a position to compromise her health by risking her competing at New Delhi," he added.
Semenya's withdrawal came as a surprise especially since it came just hours after mentor Michael Seme stated that she would be fit in time for the CWG 2010.
Among the other star runners who have pulled out of the Delhi Games include Usain Bolt, Asafa Powell, and Phillips Idowu.