ALSO READ: Reaction to the death of cricketer Phillip Hughes READ: Australia mourns cricketer Phillip Hughes' death READ: Australia's unconventional batsman Phillip Hughes Dr Peter Larkins, a leading sports physician, told Reuters: "Time is of the essence when your brain has suffered trauma."
Governing body Cricket Australia (CA) confirmed the 25-year-old had lost his fight for life, casting a pall over a cricket-mad nation which is co-hosting the World Cup early next year.
"We are extremely sad to announce that Phillip Hughes has passed away at the age of 25," CA said on its Twitter feed.
"Our thoughts go out to Phillip's family, friends, and the entire cricket community on this incredibly sad day.
"He was not in pain before he passed and was surrounded by his family and close friends.
"As a cricket community, we mourn his loss and extend our deepest sympathies to Phillips family and friends at this incredibly sad time."
Cricket Australia was due to conduct a news conference at St Vincent's hospital in Sydney at 5 pm.
The Australian flag was lowered to half-mast over the Sydney Cricket Ground where Hughes suffered the horrific injury on Tuesday when batting for state side South Australia.
He was struck on the head by a short-pitched delivery from New South Wales paceman Sean Abbott, a devastating blow that experts compared to the trauma suffered by car crash victims.
After being treated at the stadium, Hughes, who played 26 tests and 25 one-day internationals, was rushed to hospital to have emergency surgery to relieve pressure on his brain.
News of Hughes's death brought a fresh wave of tributes on social media, with past and present players conveying their shock and grief.
"No no no no no. RIP Phillip Hughes," former Australia wicketkeeper Adam Gilchrist tweeted.
Australia Prime Minister Tony Abbott described Hughes as a "a young man living out his dreams".
"His death is a very sad day for cricket and a heartbreaking day for his family,” Abbott said in a statement.
"What happened has touched millions of Australians. For a young life to be cut short playing our national game seems a shocking aberration."
The tragic announcement followed calls by former players for the Australian team to abandon the first test of the four-match series against India next week.
Former test batsman Dean Jones told Melbourne radio station 3AW he thought the December 4 match in Brisbane could not go ahead.
"I don't think any of the boys will want to play," he said.
The news travelled quickly through the global cricket community, with the Pakistan test match against New Zealand suspended out of respect for the player.
Hughes death would prove a "game-changer" for the so-called 'gentleman's game' of cricket, pundits said, ranging from the standards for head protection to the practice of short-pitched fast bowling.
Cricket balls are roughly the same shape and size of a baseball but harder and heavier. Fast bowlers regularly bowl at speeds of 140kph and short-pitched balls, known as 'bouncers', are often used as a tactic to intimidate batsmen.
Questions about the response time of ambulances dispatched to the stadium have also been raised.
The head of New South Wales Ambulance was to be hauled before the state health minister Jillian Skinner on Thursday after the ambulance authority issued conflicting statements about their response times.
The arrival of the first ambulance took 15 minutes, NSW Ambulance clarified in a statement on Wednesday.
The state's median response time for the highest priority "life-threatening cases" was just under eight minutes in 2013-14, according the authority's statistics.
Born in the small town of Macksville in New South Wales state, the pint-sized Hughes grew up on a banana plantation and made his first-class debut at 18.
He took the cricketing world by storm when he made his test debut in 2009, scoring a mountain of runs despite his unconventional technique.
Hughes would betray a vulnerability to short-pitched bowling and though he was in and out of the Australian team over the following years, he never complained publicly about his plight as a fringe player.
He had scored 63 runs before being struck on Tuesday, his last innings said to be an audition to replace injured Australia captain Michael Clarke for the first test.
ALSO READ: Reaction to the death of cricketer Phillip Hughes
READ: Australia mourns cricketer Phillip Hughes' death
READ: Australia's unconventional batsman Phillip Hughes
Dr Peter Larkins, a leading sports physician, told Reuters: "Time is of the essence when your brain has suffered trauma."