Australia batsman Phil Hughes is fighting for his life in intensive care after being struck on the head by a bouncer during a Sheffield Shield match.
Australia team doctor Peter Brukner has said there are likely to be no updates on the 25-year-old's condition until Wednesday, with Hughes in Sydney's St Vincent's Hospital on life support.
Despite wearing a helmet, Hughes - batting for South Australia - collapsed face first onto the Sydney Cricket Ground pitch, having been hit on the head after missing a pull shot off New South Wales pace bowler Sean Abbott.
Cricket Australia said on its official website that Hughes - well-known to English fans both internationally and domestically after spells with Hampshire, Middlesex and Worcestershire - had been "struck on the back, lower left side of the head".
It said no blame could be attached to Abbott, a 22-year-old who made his Australia debut last month.
"Phillip Hughes sustained a severe head injury while batting for South Australia at the SCG today," Brukner said in a statement.
"Phillip was treated on the ground by Cricket NSW medical staff and transferred by Ambulance to St Vincent's Hospital.
"He subsequently underwent surgery and remains in a critical condition in the hospital's intensive care unit.
"Unless there is any significant change there will be no further updates on his condition until tomorrow.
"Phillip is receiving the best possible medical care. The thoughts of his team-mates and the wider cricket community are with Phillip and his family and friends at this difficult time."
The left-hander, on 63 at the time, put a hand on his knee after being struck before falling face first to the ground. Play in the game was immediately suspended and the match later abandoned entirely.
He was then given mouth-to-mouth resuscitation and oxygen on the boundary line after being carried off the pitch on a stretcher.
Cricket Australia said that despite reports an air ambulance was required, Hughes was taken to St Vincent's by ambulance.
Speaking to cricketaustralia.com.au, hospital spokesman David Faktor said: "He's in ICU now, they've finished the surgery's but he's still in a critical condition. Now they'll just monitor him."
The South Australian Cricket Association's high performance manager Tim Nielsen was in the crowd with Hughes' mother and sister and went to St Vincent's, along with Australia captain Michael Clarke.
An injury to Clarke had led to talk of Hughes getting a recall for the forthcoming Test series against India. A 26-Test international, his last appearance for Australia came in a one-day international against Pakistan in October.
Hughes memorably scored two hundreds in just his second Test match against South Africa, with his last five-day appearance coming against England at Lord's last summer. In the Test prior to that he scored 81 at Trent Bridge alongside Ashton Agar in a last-wicket stand that nearly produced a memorable win.
Australia coach Darren Lehmann led the well wishers for Hughes, writing on Twitter: "Our thoughts and prayers are with phil and his family! He is a great fighter and a great young man!"
Hughes' fellow Australia international David Warner was in the field when the incident occurred and he rode alongside Hughes when he was wheeled off the field on a medicab.
He wrote on Twitter: "Thoughts are with my little mate Hughsy and his family. He is a fighter and a champion and he will get through this. Praying for you buddy."
The incident will serve as a reminder to the dangers facing batsmen against fast bowlers, despite the protective equipment available.
For now, though, all thoughts are understandably with Hughes and Cricket Australia chief executive officer James Sutherland is keen to not only support the batsmen but all those involved in Tuesday's shocking incident.
"Our thoughts and prayers are with Phil Hughes right now. We are also thinking of his family, team-mates and friends in the Australian cricket family," he said.
"His welfare is our highest priority. We're also naturally concerned about all of those involved in today's game and will be giving them our utmost support."
The England and Wales Cricket Board also sent a message of support, tweeting: "Thoughts with Phil Hughes and his family from all at ECB. Get well soon."
The touring Indian team also sent their best, saying in a statement: "We join with the rest of the cricket community around the world to offer our support and prayers to Phil and his family as well as our friends within Australian Cricket."
Cricket helmet manufacturers are doing all they can to prevent head injuries in the sport, according to a former player who now works as a leading equipment retailer.
But according to Chris Taylor, the former Yorkshire batsman who now runs leading retailer All Rounder Cricket in Leeds, little can be done to protect that area of the body.
"I know cricket manufacturers and helmet manufacturers are working all the time to improve the safety of helmets and I know a new British safety standard has been launched in the UK for the 2015 season where helmets have to have fixed grills," Taylor, a former England Under-19 international, said.
"I guess it's part of the job, at some stage somebody is going to hit on the head.
"The helmet doesn't protect all of the head, there's a gap for your eyes, there's a gap where your neck is, so you have to expect some blows at some stage and this is very unfortunate for Phil Hughes."
Simply extending the helmet so that it covers the neck is impractical, Taylor believes.
"Once the helmet starts trying to cover the neck as well, if that's where Phil Hughes has been hit, it's going to restrict your movement as a batsman," he added.
"You need to be able to move quickly so if it's restricting your head and your neck, we could get to the stage where you just wear full body armour because at the end of the day you can get a blow on your chest that can cause you serious problems.
"My understanding is it's hit him at the worst possible place at the wrong angle and it is extremely unlucky."
England and Wales Cricket Board guidelines stipulate that helmets should be worn by all batsman under the age of 18, while senior players rarely revert to age-old traditions of batting in caps.
Taylor insists that all the relevant bodies are working hard on safety, but that from time to time accidents will happen.
"I work closely with some of the helmet companies and they are always working, they have to achieve this British safety standard," he said.
"There comes a stage when you can't protect any more of the body without being able to move. I know the ECB has taken steps forward but it's part of the game, but you've got to be able to move so what lengths do you go to in order to cover a person's body?"
Hughes was batting while wearing a helmet made by Masuri and the company has said it will be releasing a statement later on Tuesday.