American former Olympic and world 400m champion Jeremy Wariner will miss this month's World Championships in South Korea because of a foot injury.
The 27-year-old, a key player in the US Olympic and world 4x400m relay wins, tore a ligament in the second toe of his left foot while training in July.
"Right now my focus is to get healthy, prepare for next season, and try for my second 400m Olympic gold," he said.
The injury will not require surgery but may take 12 weeks to recover from.
Wariner, the world's top-ranked 400m runner in 2010, has been plagued by minor injuries this season.
He has clocked just the 12th fastest time this year, and was beaten in the US Championships - which double as the national world trials - by college athlete Tony McQuay.
Wariner won the Olympics 400m title in Athens, in 2004, and followed that with World Championships wins in 2005 and 2007.
He was runner-up to fellow American LaShawn Merritt at the 2008 Olympics and 2009 World Championships.
Wariner is expected to be replaced on the US team by fourth-placed trials finisher Jamaal Torrance at the World Championships, which take place between 27 August and 4 September.