Olympic women's marathon champion Peres Jepchirchir and distance runner Francine Niyonsaba have been ruled out of this month's World Athletics Championships.
Kenyan Jepchirchir will miss the event in Eugene, Oregon, with a hip injury, while Burundi's Niyonsaba has a stress fracture.
An Olympic silver medallist over 800m in 2016, Niyonsaba had been entered for the 5,000m and the 10,000m after the 29-year-old was banned from competing in her favoured distance in 2019 owing to her overly-high testosterone levels.
Jepchirchir, 28, won the Olympic title in Tokyo last year in a time of two hours 27 minutes and 20 seconds, beating compatriot Brigid Kosgei and American Molly Seidel to take gold.
"The hip and the whole leg is painful," the 2016 and 2020 World Half-Marathon Championships winner told Kenyan news outlet 'The Nation'.
"I am so disappointed but I would rather not aggravate the injury since we still have another world event next year before my Olympic title defence at the 2024 Paris Games."
Jepchirchir won on her Boston Marathon debut in April and was a late addition to Kenya's four-strong team for the women's marathon in Eugene.
Reigning world champion Ruth Chepngetich will race alongside Judith Jeptum and Angela Tanui.
Niyonsaba, meanwhile, said she had "no choice" but to withdraw from the championships on American soil.
"About one month ago, I had a beginning of a stress fracture. Me and my team did everything possible to recover," she said in a post on Instagram.
"I am almost ok now but I couldn't train for all this period, so I'm not in the shape that can allow me to perform the way I wanted."
Niyonsaba, the only Burundian woman to win an Olympic medal, won over 3,000m at the Doha Diamond League in May.
At last year's Olympics, she finished a creditable fifth in the women's 10,000m final, with a national record, as she impressively adjusted to her ban from competing between 400m and 1500m because of naturally-high levels of testosterone.
The World Athletics Championships begin on Friday and last until 24 July.