Wayde van Niekerk secured his spot at the Tokyo Olympics after producing a qualifying time of 44.56 seconds at a World Athletics Continental Tour event in Madrid.
The 28-year-old Olympic champion can prepare for his title defence in Japan after completing his first 400m race in 2021, but it was a day to forget for Caster Semenya.
The two-time 800m gold medallist was looking to qualify via the 5000m in Regensburg, Germany, and needed a time of 15 minutes and 10 seconds (15:10.00) in order to make it to Tokyo.
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However, the 30-year-old finished fourth in a time of 15:57.12 and will now run in Liege, Belgium on June 30.
Sha'Carri Richardson booked her place for Tokyo after running 10.86 to win the women's 100m at the US Olympic track and field trials.
Javianne Oliver (10.99) and Teahna Daniels (11.03) finished second and third respectively.
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