Simone Manuel, the defending Olympic champion in the women's 100-meter freestyle, finished ninth in the event's semifinal Thursday night at the U.S. Olympic Swimming Trials, failing to advance to the final. 

Manuel went 54.17, .02 seconds out of the eighth-place finish she needed to advance. Olivia Smoliga and Natalie Hinds are the top seeds for the final, tying at 53.55 seconds.

Manuel will have one more shot to qualify for Tokyo in the 50-meter freestyle over the weekend; she's the reigning world champion in the event. 

When Manuel tied Canada's Penny Oleksiak to win the 100 in 2016, she became the first Black woman in swimming history to win an individual Olympic gold medal. Manuel set the American record in her swim in Rio as well as when she won at worlds in 2017 and 2019. 

Manuel declined to do a post-race TV interview, however, it was revealed on the NBC broadcast that she took three weeks out of the pool from the end of March until mid-April for a variety of reasons, none of which were said to be injury-related. NBC announcer Mike Tirico alluded to a number of factors in Manuel's decision, including exhaustion related to the COVID-19 pandemic and the ongoing reckoning around racial injustice in the United States. 

"Simone Manuel being one of the few -- not just in America but in the world -- elite Black swimmers, after winning the gold in Rio, she became the person always asked about that topic," Tirico said. "So Simone has had a difficult stretch. That's part of her walking away from the training for three weeks." 

Manuel was also entered in the 200-meter freestyle earlier in the meet, but scratched. Even without racing the event individually, she could be considered for a spot on the 4x200 free relay in Tokyo if she makes the team in other events. 

Update: In a press conference after racing Thursday, Manuel said she was diagnosed with "overtraining syndrome" in March and had experienced insomnia, anxiety and depression, among other symptoms.