|Mulaudzi celebrates winning the 800m Men's Final at the 2009 world championships in Berlin [EPA]
Men's 800-meter world champion Mbulaeni Mulaudzi will not defend his title at the upcoming world championships because of a hamstring injury that will keep him out for the rest of the year.
South Africa's athletics federation said on Wednesday that Mulaudzi will miss this month's worlds in Daegu, South Korea after he failed to recover from a hamstring problem that was now affecting his lower back.
"I need to take this injury seriously so I can be ready for the Olympics next year," Mulaudzi said in a statement, adding he will sit out the rest of the season to allow him to fully recover for 2012.
Mulaudzi won the 800 title at the 2009 worlds in Berlin, but had been hampered by hamstring problems through most of this season.
The 30-year-old former world indoor and Commonwealth Games champion missed the South African nationals at the start of the season and had managed just one solid performance in 2011 - a second-place finish at the Diamond League meet in New York in June.
Mulaudzi's coach, JP van der Merwe, said the previous hamstring injury had flared up again and treatment had not worked.
The worlds start on August 27.
Mulaudzi's victory in Berlin was his first outdoor world title, but the achievement was overshadowed by fellow South African Caster Semenya, who won the women's 800 as a teenager and amid a storm of controversy over gender tests.
| Vlasic has dominated women's high jump since claiming gold in the 2007 worlds [EPA]
World high jump champion Blanka Vlasic could also miss the world championships because of a hamstring injury, the Croatian said on her website on Wednesday.
Vlasic, 27, said she would announce her final decision on Friday after learning the full results of last Saturday's scan which revealed a partial rupture of her left hamstring.
"The scan was taken after constant pain which hampered high-intensity training and (on Tuesday) morning, the doctor confirmed a partial semimembranosus rupture," she said.
"The situation puts in doubt Blanka's participation in the world championships in South Korea and the final decision will be made on Friday."
Vlasic has dominated the women's high jump after winning gold at the 2007 world championships in Osaka.
She repeated the feat at the 2009 event in Berlin and also won the 2010 European title in Barcelona. She won a silver medal at the 2008 Beijing Olympics.
Vlasic set a personal best of 2.08 metres in Zagreb in 2009, just one centimetre short of Bulgarian Stefka Kostadinova's 1987 world record.