Yohan Blake out of World Championships with injury

Reigning world 100m champion Yohan Blake has withdrawn from August's World Athletics Championships in Moscow with a hamstring injury.

The 23-year-old Jamaican pulled out of his country's national championships last month having been troubled by the injury since April.

Blake won the 2011 title in Daegu, when compatriot Usain Bolt false-started.

Compatriot Asafa Powell and American Tyson Gay have withdrawn from the event in Moscow after positive dope tests.

Gay's A sample from an out-of-competition test in May was positive, while Powell tested positive for a banned stimulant at the Jamaican Championships, which took place on 20-23 June. Both athletes are awaiting the results of their B samples.

As defending champion Blake was handed an automatic place in the 100m at this year's World Championships, but he would not have run the 200m in Moscow after pulling out of the Jamaican trials and therefore failing to qualify.

Blake has not run a competitive 100m this year and laboured to a time of 20.72 seconds over 200m in Jamaica on 8 June.

"This decision was made after continual assessment and re-evaluations since his withdrawal from the Jamaican Senior Championships," said Blake's manager Cubie Seegobin.

"Yohan has made vast improvement, although the injury sustained in April of this year has prevented him from attaining the necessary fitness levels that we have grown accustomed to seeing in his competition performances."

Gay recorded the fastest time in the world this year when he ran 9.75 seconds in Iowa in June.

Jamaica's Nesta Carter recorded the quickest time of the year of the athletes still set to run in the World Championship 100m when he clocked 9.87 in Madrid on 13 July.

Twice-banned American Justin Gatlin is next fastest with 9.89, while Britain's Jason Dasaolu set a personal best of 9.91 with a stunning performance at the British Championships last Saturday.

Olympic champion and world record holder Bolt booked his place in Moscow when he won the Jamaican trials in 9.94 seconds - his fastest time this year.