Johannesburg - Defending women's 800m world champion Caster Semenya withdrew from the World Student Games held in Shenzen, China from August 12 to 23 due to a niggling back injury.
Her withdrawal from the student games was confirmed by University Sport South Africa's (USSA) athletics chairman Glen Bentley on Thursday.
Bentley said Semenya informed USSA on Sunday she could not join the team that left for China on Wednesday.
He said the athlete met with the team manager Jerome Walters and the team coach Mohamed Ally and told them she did not want to risk injuring herself before the world championships.
"We decided that the world championships was a more serious competition, and we support her sitting out because it is in the national interest," said Bentley.
Bentley, however, said it was disappointing to lose Semenya as she was a definite medal contender.
The persistent injury could be a blow for the 20-year-old as she has little over two weeks left before she defends her title at the world championships in Daegu, South Korea.
Semenya had this year been struggling to find consistency with her performances.
Out of the 13 races she had competed in this year, she only twice dipped under two minutes in the two-lap race.
Her best this year is 1:58:61 which she ran at the Oslo Bislett Games in early June but could not reproduce this performance in her last four races.
At the end of last month Semenya finished in eighth place at the Stockholm Diamond League meeting where she posted a time of 2:01.28.
This time is a long way outside her personal best of 1:55.45 she ran at the world championships in Berlin two years ago.
Despite her fluctuating performance Semenya said in a statement less than two weeks ago that she was confident of improving the 800m and 1 500m world records.
She would, however, need to run more than two seconds faster than her South African record to improve Jarmila Kratochvilova's 28-year-old global mark.