Caster Semenya's first appearance in a world championships in five years on Wednesday saw the controversy-mired South African fail to qualify for the women's 5000m finals.
In roasting mid-afternoon temperatures, Semenya finished 13th in the first of two rounds at Hayward Field, Eugene, in 15:46.12, more than 45sec off the 15th and final qualifying place.
"Cooking!" said Semenya post-race. "It was hot, I could not keep up with the pace, I tried to stick as much as I can, but you know, it is a part of the game.
"I think it is great to be able to run here," she added. "Just being able to finish the 5k, for me, it is a blessing. I am learning and I am willing to learn even more."
Her time was far off the heat-winning 14:52.64 set by Ethiopian Gudaf Tsegay, fresh from her silver in the 1500m.
Semenya sat 13th of the 18-strong field as Japan's Kaede Hagitani set the early pace in her heat.
When a nine-strong pack broke clear, Semenya would not be part of the breakaway and she quickly fell to a full 80 metres off the lead with 2km to go.
That has increased to a clear 100 metres as American Karissa Schweizer hit the lead with three laps to run.
Tsegay kicked and led a pack of five through the bell with Semenya a distant figure 300 metre off the pace.
The South African last competed at world championships in London in 2017 where she won her third 800m world crown.
A year later she won double gold in the 800m and 1500m at the Commonwealth Games which was the last time she represented South Africa in a global international competition.
Semenya was forced to switch from her favoured distance to the longer event due to gender eligibility rules that required her to take testosterone-reducing drugs to compete in races between 400m to a mile.
World Athletics bars women athletes with high testosterone levels from competing in shorter races because the governing body says the hormone increases muscle mass and oxygen uptake.
Semenya, who became a world champion at 18 years of age in Berlin in 2009, has made several unsuccessful legal attempts to overturn the ruling.
"She's eligible to be here," Coe said of Semenya, who initially missed qualification when she only finished sixth at the African Championships last month, but benefitted from a number of athletes dropping out.
Joining Tsegay in Saturday's final will be Ethiopian teammates Letesenbet Gidey, the 10,000m winner here, and Dawit Seyaum and Ethiopian-born Dutch runner Sifan Hassan, the reigning Olympic champion over 5000m.
Also going through were the Kenyan trio of Margaret Chelimo Kipkemboi, Gloria Kite and Beatrice Chebet, Britons Eilish McColgan and Jessica Judd, and three Americans in Schweizer, Emily Infeld and Elise Cranny.
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