Broadcaster Alan Jones has arrived at St Vincent's Hospital to visit injured batsman Phillip Hughes, who remains in an induced coma in St Vincent's Hospital after being struck on the head by a cricket ball.

Australian players have been rallying around Hughes throughout the morning.  Aaron Finch, Matthew Wade and Peter Forrest flew to Sydney from interstate to be by the stricken 25-year-old's bedside as he fights to survive a catastrophic bleed on his brain.

David Warner, who was one of the first to rush to his friend's aid when he collapsed at the crease of the Sydney Cricket Ground on Tuesday, arrived at the hospital about 11am.

Australian captain Michael Clarke was there as each player arrived - he has been a constant presence at the hospital since the accident at the Sydney Cricket Ground on Tuesday afternoon.

Clarke got to St Vincent's about 6am on Thursday, after leaving the previous evening about midnight.

Hughes' father, mother and sister are also keeping vigil at the hospital. His mother and sister were in the crowd at the SCG watching Hughes' innings when he was struck.

Hughes, who turns 26 on Sunday, remains in a critical condition in the hospital's intensive care.

A steady stream of cricketing identities has made the trip to be by Hughes' side, including Brett Lee, Shane Watson, Mitchell Starc, Phil Jacques, Brad Haddin and Steve Smith.

The South Australia-NSW Sheffield Shield match was abandoned on Tuesday following the accident, and Cricket Australia called off the other two shield games in Brisbane and Melbourne on Wednesday after consulting players and the Australian Cricketers' Association.

"Given how players across the country are feeling right now, it's just not the day to be playing cricket and we understand that," Cricket Australia general manager of team performance Pat Howard said.

Hughes suffered catastrophic bleeding in his brain in the freak cricket accident, in which his skull was fractured after he was struck by a ball on a vulnerable part of his head not protected by his helmet.

The fracture occurred near the large vessels that transport blood to the brain, damaging one, which quickly caused heavy bleeding.

Such subdural haematomas are dangerous not only because the pressure caused by the blood pooling in one place can crush the brain, but also because it blocks blood from entering to provide the brain with the oxygen it needs to survive.

Questions remain about why it took more than an hour from when Hughes was struck by the ball at 2.23pm until he arrived at St Vincent's Hospital for emergency surgery.

A leading Sydney emergency doctor, who declined to be named, said it appeared a substantial amount of time was spent stabilising Hughes at the site of the accident, rather than getting him to hospital where he could be treated.

"It is not isolated to this case. It's surprising how long transport time can be," he said. "Stabilisation doesn't mean [they are] attempting a cure."

Large hospitals were used to treating bleeds on the brain, he said.

"[In regional hospitals] we don't really see major trauma like that, but at a city hospital like St Vincent's it is not uncommon."

Fairfax Media understands Hughes' neurosurgeon was Malcolm Pell, who performed life-saving surgery on Parramatta Eels star forward Adam Ritson, whose life-threatening brain cyst was discovered in a CAT scan after he was concussed by a high tackle in 1996.

Earlier this year, he treated 23-year-old one punch victim Michael McEwen.

Hughes, the South Australian opener, was struck on the head by a bouncer bowled by NSW paceman Sean Abbott during the afternoon session of the shield match at the SCG.

NSW team doctor John Orchard worked on Hughes while he was still on the ground.

Hughes was taken off the field and received CPR and mouth-to-mouth, before being taken to St Vincent's in a critical condition.

He had emergency surgery to relieve the pressure on his brain.

On Wednesday morning, doctors carried out more brain scans.

Australia team doctor Peter Brukner said later that Hughes' condition was unchanged and he remained critical.

"We will let you know of any further developments," he said.

The NSW squad convened at the SCG and were addressed by coach Trevor Bayliss, a psychologist, and Cricket NSW chief Andrew Jones. They were told to handle the situation in whatever manner they felt appropriate.

Cricket Australia offered counselling for Australian and Sheffield Shield players.

Cricket Australia chief James Sutherland said players and support staff were suffering.

"Obviously it's difficult for them," he said on Wednesday.

Hughes was a popular player, not just in Australia but around the world and everyone was feeling for Hughes and Abbott, Mr Sutherland said.

To help deal with the overwhelming level of interest, Cricket Australia has set up a page on its website for people to leave messages for Hughes and Abbott.

Meanwhile, the president of the Northern District Junior Cricket Association Philip Azize called for the introduction of a compulsory time-out rule after any hit to the head.

"I've already fired off an email to all clubs, managers, delegates and parents, saying helmets are compulsory," Mr Azize said.

Hughes' plight resonated around the globe, with messages of support flooding social media.

Hughes held the top position in social media in Australia, the United Kingdom, India and South Africa.

He was the second-most talked about topic on Twitter globally for more than an hour on Tuesday evening.