Sprinter Lachlan Kennedy and Olympic race walking medallist Jemima Montag have been ruled out of Australia's team for the athletics world championships in Tokyo.
Kennedy, who became the second Australian to break the 10-second barrier in the 100 metres in May, succumbed to a stress fracture in his lower back.
"It's with a heavy heart I have to announce that I will not be competing at this year's world championships in Tokyo due to a progressing injury," the 21-year-old wrote on social media.
Montag, who won two bronze medals at the Paris Olympics, suffered a recurrence of a hamstring injury at a training camp in Switzerland this month and had decided to have surgery, Australian media reported.
The rehabilitation period is likely to sideline Montag for months.
The injuries are a blow for an Australian team that has enjoyed a resurgence in track and field in recent years.
Australia won seven medals at Paris, their best athletics haul since the 1956 Melbourne Games.
The world championships start in Tokyo on 13 September.