Jamaica's former world 100 meters record holder Asafa Powell tested positive for a stimulant at last month's national championships, his agent said.
World record holder Powell clocked 10.01 seconds in the quarter-final heats while Gay won his heat in 10.06.
American Tyson Gay surged past Jamaica's Asafa Powell to win gold in the men's 100 meters at the world championships.
The coach of Jamaican sprinters Asafa Powell and Sherone Simpson said on Tuesday they were not to blame after the Olympic medallists failed dope tests.
Powell feels that hitting sixes for fun is the new normal.
Out of the two world records held by track superstar Usain Bolt, his 100m dash timing of 9.58 seconds stands more likely to be broken than the 200m mark of 19.19secs, his fellow Jamaican sprinter Asafa Powell said on Friday.
Chris Xuereb, the masseur and fitness advisor of Asafa Powell and Sherone Simpson, has denied providing the two Jamaican sprinters with performance-enhancing drugs and said they should take responsibility for their failed dope tests.
Tearful former double sprint world champion Tyson Gay said on Sunday he has tested positive for a substance he could not identify and is pulling out of next month's world championships in Moscow.