Allyson Felix will concentrate on maximising her chances of winning the women's 400 metres after narrowly failing to qualify for the 200m at the Rio Olympics.
Felix finished fourth at the United States Olympic team trials for track and field in Eugene on Sunday, 0.01 seconds behind third-placed Jenna Prandini, who claimed the final berth after a photo finish.
USA Track and Field had successfully lobbied for a change to the schedule of next month's Games to increase Felix's chances of producing a competitive performance in both the 200 and 400m.
However, an ankle injury suffered in May affected her preparation for the trials.
And although Felix secured her ticket to Brazil by winning the women's 400m in Oregon, the 30-year-old will not be able to defend the 200m gold she won in London four years ago.
"I'll just take the time we have to get back and perfect the 400," she said.
"I mean, the speed just wasn't there. When I give all I have and I run 22.50 [sic, 22.54], the speed just wasn't there."
Felix, who has four gold and two silver medals from three Games, having made her debut in Athens in 2004, was able to temper her disappointment with the knowledge the injury has not prevented her from securing a place at what will be her fourth successive Olympics.
"I could only do what I could with the ankle," she said.
"[I'm] honestly disappointed, you know?
"The whole year, that has been what I was working for. When I look back and see everything that happened, I still think it's quite amazing I was able to make the team."
Tori Bowie and Deajah Stevens, together with Prandini, will contest the women's 200m for the United States in Rio.