2012 Olympic 800-meter silver medalist Nijel Amos has withdrawn from competition at the IAAF World Championships in Moscow due to a nagging quad injury from earlier in the season. On July 19, Amos won a gold medal at the World University Games' 800-meter run. His winning time of 1:46.53 is far from his personal best of 1:41.73, which is tied for the third in all-time history with Lord Sebastian Coe. 

The personal best comes from the Olympic final, where David Rudisha broke his own world record in London. With Rudisha not competing due to a knee injury, the competition in Moscow will be without the Olympic gold and silver medalists. 

Following Amos' news, Nick Symmonds put out the following tweet. 

Symmonds (1:43.67)  expects to contend for a medal in Moscow along with current world leader Duane Solomon (1:43.27). Mohamed Aman of Ethiopia (1:43.33) and Ayanleh Souleiman  of Djibouti (1:43.63) pose the biggest international threats as they have run the second and third fastest times of 2013.

The first round of the men's 800-meter dash will take place on August 10.