The 23-year-old Irish sprinter crossed the line in 52.26 seconds, well below the standards she has set in recent years and significantly slower than her previous outing at the same meeting, where she finished fourth in 51.33 seconds.
Competing in lane three, Adeleke made a promising start and remained in contention through the opening stages of the race. However, she began to lose momentum around the final bend before fading considerably over the closing 100 metres, eventually finishing at the back of the field.
The race was won by Jamaica's reigning NCAA champion, Dejanea Oakley, who posted a winning time of 49.64 seconds, while last year's NCAA champion, Aaliyah Butler, finished second in 49.97 seconds.
The Eugene meeting marked Adeleke's first competitive 400m race since this event 12 months ago. Before Saturday's outing, she had competed only three times this season, recording an Irish indoor best of 36.30 seconds over 300 metres in February, running a leg in a 4x400m relay in Texas in early April and posting 22.86 seconds in a 200m race later that month.
Her latest performance is her slowest over the 400m distance since January 2022, when she was beginning to focus more seriously on the event as a teenager.
With just over five weeks remaining before the European Championships in Birmingham, Adeleke remains outside the automatic qualification standard of 51.20 seconds. She is expected to have another opportunity to achieve that mark when she competes at the Monaco Diamond League next Friday.
Adeleke enjoyed a breakthrough campaign in 2024, claiming silver in the 400m at the European Championships in Rome before narrowly missing out on an Olympic medal with a fourth-place finish at the Paris Games. However, the Irish star found it difficult to reproduce that level of performance in 2025, a season that was disrupted by injuries.
After withdrawing from the Tokyo World Championships, Adeleke revealed the extent of the physical setbacks she had been managing.
“Several different injuries, from hamstring to groin to knee,” she told RTÉ last December.
She added:
“We are just trying to make sure that everything is managed and maintained.”
Adeleke has been coached by Edrick Floreal since relocating to Austin in 2021 to attend the University of Texas. She has continued to train there after turning professional in 2023.
Meanwhile, fellow Irish Olympian Cathal Doyle finished eighth in the men's 1,500 metres at the Meeting Stanislas Nancy in France, clocking a season's best of 3:33.52—just 0.02 seconds outside the automatic qualifying standard for the European Championships.
Attention will now turn to Sarah Healy, who is set to compete in the women's mile on the second day of the Eugene Diamond League, with the race scheduled for Saturday evening.