Jamaica have left national 200m champion Steve Mullings out of their team for the World Championships in South Korea, which start on 27 August.
Mullings, 28, is the third fastest man in the world over 100m in 2011.
Officials said he had been left out because of the "outstanding issue surrounding Mr Mullings".
The Jamaica Anti-Doping Commission said last week that a Jamaican track and field athlete had tested positive at trials but did not release a name.
The Jamaica Athletics Association said in a statement on Mullings: "However, if the matter is resolved in his favour, there is a provision where he can be re-instated."
Mullings, a member of Jamaica's gold medal-winning 4x100m relay team at the 2009 World Championships in Berlin, won the 200m and finished third in the 100m at the Jamaican trials in June.
He had been expected to join defending champion Usain Bolt in the 100m and 200m in Daegu and help Jamaica defend their 4x100m relay title.