England opener Marcus Trescothick is returning home from England's Ashes tour to Australia after suffering a recurrence of a stress-related illness.
Trescothick was short of runs in England's opening tour games
The stunning news comes just nine days before the start of the five-match series in Brisbane.
"We are naturally disappointed to lose a player of his quality from our Ashes squad," said coach Duncan Fletcher.
"Everyone in the dressing room hopes that he is able to make a full recovery and resume his cricketing career."
Trescothick played in England's opening tour games against a Prime Minister's XI in Canberra and New South Wales in Sydney, but managed only 10 runs in two innings.
And following discussions with team management and medical staff, it was agreed he should fly home as soon as possible.
The 30-year-old's problem first appeared during the tour to India earlier this year and he continued to struggle with it over the summer, despite making a century in the first Test against Sri Lanka at Lord's in May.
Trescothick also hit one-day hundreds against Sri Lanka and Ireland but struggled in the Tests against Pakistan in the second half of the summer and opted out of the recent Champions Trophy tournament in India.
Last week he admitted he fell out of love with cricket for a time but, looking ahead to the Ashes series, told BBC Sport: "I feel good - I'm itching to get going."
"Having watched the guys out in India, the excitement when the team gets a wicket, I want to get back out there.
"When you've have had a rest it rekindles the buzz you've longed for all your career."
Alastair Cook now looks certain to make his Ashes debut in Brisbane
His return home simplifies England's selection situation for Brisbane.
Fletcher and skipper Andrew Flintoff were facing the prospect of being able to pick only two from Alastair Cook, Ian Bell and Paul Collingwood, even though all three have been in excellent form this year in Test cricket.
Cook now seems certain to replace Trescothick as Andrew Strauss' opening partner, with Bell likely to bat at three and Collingwood at five.
However, the loss of the most experienced player in the squad is bound to disrupt preparations for the final Test warm-up game against South Australia, which begins in Adelaide on Friday.
Trescothick has scored more than 5,800 runs in 76 Test appearances at an average of 43.8.
His record against Australia is less convincing and he has not managed a single Test century against them in three previous series.
An England and Wales Cricket Board statement said the selectors would hold "urgent discussions" in the next 24 hours about replacing Trescothick in the tour squad.
The most obvious replacements would be Robert Key, Owais Shah or Ed Joyce, who have all been picked for the Academy squad in Perth.
Meanwhile, Trescothick's club, Somerset, were quick to offer him support.
Chief executive Richard Gould described him as "one of the most talented players the county has ever produced".
And he told the club's website: "It is evident Marcus needs more time and space to recover.
"Somerset CCC will work with the ECB in order to ensure that he is provided with everything he needs."