2012 Olympic 800-meter silver medalist Nijel Amos has withdrawn from competition at the IAAF World Championships in Moscow due to a nagging quad injury from earlier in the season.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. 

Sad to hear about all of the injured 800m runners this year. Wishing them quick recoveries. My durability is finally coming in to play!

— Nick Symmonds (@NickSymmonds) July 29, 2013

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.