Olympic 100m silver medallist Sha'Carri Richardson underwhelmed in her season opener in Tokyo on Sunday, finishing fourth in 11.47sec four months before the world championships are held in the same stadium.
The American, who ran with strapping on her lower right leg, was slow out of the blocks and never led the Golden Grand Prix women's 100m, which was won by Australia's Bree Rizzo in 11.38.
American Twanisha Terry, fifth in last year's Olympics, was second in 11.42 followed by Canada's Sade McCreath in 11.46.
World champion Richardson will attempt to defend her title in the Japanese capital in September.
"It's a season-opener for those athletes and they will be very, very strong come the world championships," said Rizzo.
"I really look up to those athletes so to come out on top was pretty exciting for an Australian athlete."
Christian Coleman, Richardson's boyfriend and training partner, finished third in the men's 100m in a time of 10.11sec.
Japan's Hiroki Yanagita won the race in 10.06, followed by American Christian Miller in 10.08.
"Each race, every opportunity I have is more of a mental, internal battle for me to get better," said Coleman, the 2019 100m world champion.
"I felt some good things today and I want to just keep getting better at it."
Ukraine's world and Olympic champion Yaroslava Mahuchikh won the women's high jump with a leap of 1.96m, far below her world record of 2.10m.
She also won at both Diamond League meetings in China at Xiamen and Shanghai/Keqiao in the past month.
"I'm satisfied with this competition," said Mahuchikh.
"Of course the result is not good but I'm happy with that because my body is not ready to jump high today."
Japan's world and Olympic champion Haruka Kitaguchi won the women's javelin with a throw of 64.16m.
American Robert Gregory won the men's 200m in 20.24sec ahead of Canada's Andre De Grasse, who won gold at the same stadium at the pandemic-postponed Tokyo Olympics in 2021.