Sha'Carri Richardson advanced to the Olympic women's 100m final on Saturday but was forced to settle for second place in her semi-final behind rising Saint Lucia sprint star Julien Alfred.
Richardson, the American reigning world 100m champion who is regarded as favourite for the gold medal, clocked 10.89sec to reach the final later Saturday at the Stade de France.
But the 24-year-old Texan was left trailing in the wake of Alfred, who is chasing a first ever Olympic medal for Saint Lucia.
Alfred, 23, who has never finished on the 100m medal podium at a major outdoor championships blasted home in first place with a time of 10.84sec.
There was a major surprise before the semi-final after Jamaica's two-time Olympic 100m champion Shelly-Ann Fraser-Pryce scratched from the competition.
The 37-year-old five-time world 100m champion had been chasing a record fifth consecutive medal in the Olympic 100m, 16 years after winning gold in Beijing.
Richardson and Alfred will be joined in the final by Melissa Jefferson of the United States, who finished first in her semi in a time of 10.99sec, just pipping the Ivory Coast's Marie-Josee Ta Lou-Smith, second in 11.01 sec.
But there was no final berth for Britain's European champion Dina Asher-Smith, who could only finish fifth.
"I'm just disappointed because I'm in great shape and have been in great shape all season, I fully expected to make that final, the race wasn't even fast," Asher-Smith told the BBC after her race.
Asher-Smith's compatriot Daryll Neita will feature in the final after finishing second in the third and final semi-final behind Jamaica's Tia Clayton.
Clayton led from start to finish to cross in 10.89sec, with Neita second in 10.97sec.
Twanisha Terry of the United States and Switzerland's Mujinga Kambundji reached the final as the next two fastest finishers.
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