The absence of walker Jared Tallent due to a hamstring injury at the athletics world championships has deprived the Australian team of its most reliable source of medals.
Since 2008, the 32-year-old Tallent has finished on the podium in the 50km race at every Olympics and world championships with the exception of the 2009 world titles in Berlin.
Even though first-time fatherhood and injury problems had impacted on his build up to the London championships, he was still fancied to challenge for a medal.
At the halfway stage of the 10-day championships, the only top-eight performance from an Australian has been Kurtis Marschall's seventh-placed finish in the men's pole vault.
Australia's best medal shots are on the final weekend with Sally Pearson in the 100m hurdles, Dani Stevens in the women's discus and Dane Bird-Smith in the men's 20km walk.
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Until Tuesday, that group of genuine top-three contenders had also included Tallent.
"2017 has been a remarkable year for me," he said in a statement from his altitude training base in Switzerland.
"On the one hand, my wife and I excitingly welcomed our son, Harvey, to the world and we could not be happier.
"On the other, I have been challenged in my race walking, with recurring injuries and now a hamstring complaint that will prevent me from being able to start."
All four of the walks at the world championships will take place on Sunday.
Tallent's wife Claire will compete in the women's 20km race, less than three months after giving birth.
"The decision to withdraw is never easy, but the good news is that I will have the chance to cheer on my wife, Claire," said Tallent.
" ... it will be a privilege to support her in the way she has supported me so many times before."
Australia will now be unrepresented in the men's 50km walk in London.
