Olympic BMX cycling hopeful Kai Sakakibara is in a medically-induced coma in Canberra Hospital after sustaining serious head injuries in a race accident on Saturday.
The 23-year-old underwent surgery on Sunday morning to relieve pressure on his brain.
Described as being in a critical but stable condition, Sakakibara is expected to remain in a coma for the next fortnight.
Sakakibara, ranked among the world's top-10 riders in recent years, and his younger sister Saya are aiming to make their Olympic debuts in Japan, where he spent part of his childhood after being born on the Gold Coast.
"We understand the road ahead will be a long and difficult one, we are staying positive and taking things day by day," a statement from Sakakibara's family read on Wednesday.
"There isn't much we can do at this point, but Kai needs your support and your positive energy sent his way.
"Please keep thinking of Kai ... and stay with us on his journey for the months ahead."
Update on injured BMX rider Kai Sakakibara from his family.— Dominique Loudon (@dloudon9) February 12, 2020
An operation on Sunday relieved some pressure on his brain.
Kai’s condition is described as critical but stable, we are expecting he will remain in a medical coma for the next two weeks or so.@9NewsGoldCoast pic.twitter.com/mHeSGVcOGy
Sakakibara injured in horror crash
Sakakibara fell on the second corner during his opening-round heat at a World Cup event in Bathurst and was treated on site by paramedics and a doctor before he was airlifted to hospital.
He began racing as a four-year-old, moving to Tokyo in 2000 and collecting multiple national titles before returning to Australia in 2008.
Sakakibara's parents Martin and Yuki said their son's BMX career was "on hold for now" as they focused on his long-term rehabilitation.
"We would like to thank everyone for the kind messages, prayers and thoughts regarding Kai," they said.
"It's amazing to know he has touched so many people."
Riders at the BMX Supercross World Cup in Bathurst, Australia salute fellow rider Kai Sakakibara by spelling out his name. The Australian and Tokyo 2020 hopeful suffered a head injury during his run yesterday and is in a "critical but stable condition" in hospital. https://t.co/XNjCnIMra7— Jo Gunston (@sportsliberated) February 10, 2020
#KaiFight77 A message regarding Kai Sakakibara from his family; Martin, Yuki and Saya.— AusCyclingTeam (@AusCyclingTeam) February 11, 2020
Please keep thinking of Kai Sakakibara and stay with his family on his journey over the months ahead.
📲 https://t.co/dihoFXFEM0 pic.twitter.com/3OzKI5IsrV