John McCarthy, as a footballer, made those he played with smile easily and often. He made them feel better about themselves and feel deeply for him.

In his sudden and tragic death in Las Vegas yesterday McCarthy - or J-Mac as those he played with knew him - has left many more football communities across the country feeling a deep sadness.

A Port Adelaide player by way of Collingwood and Sorrento, McCarthy had flown out of Australia at the weekend after the club best and fairest, one of a group of 10 Port players doing as modern AFL players do and unwinding after the season in Vegas.

At some point during the time there, the group fragmented and did their own things. McCarthy was not with his teammates when he fell from a hotel and died.

Details of how the 22-year-old player died remain thin, with certainty only that he was found in the driveway of Las Vegas hotel, the Flamingo, after a fall.

The Flamingo was not the hotel McCarthy had been staying at and no one was yesterday quite certain how or why he came to be there when he fell and died about 5.40am local time.

McCarthy was taken to the University Medical Centre, where he was pronounced dead. The incident is being investigated by the Nevada Clark County Coroner's Office.

Early yesterday Port Adelaide CEO Keith Thomas received a telephone call from the club's doctor in France saying he had just heard on French radio that a Port Adelaide footballer had died in Las Vegas. Mr Thomas had only minutes previously received the awful news from Victoria Police.

''Just how it happened seems bizarre,'' Mr Thomas said. ''At some stage John and the group separated. They [the other 10 players there] are unsure when that happened. He ended up somewhere else on his own; it was a bit weird. I believe there were witnesses on the ground when the accident occurred. The police are trying to piece together what happened.''

Port Adelaide immediately sent football manager Peter Rohde to the US to meet the players there as well as one of McCarthy's three sisters and an Australian embassy official.

The players in Las Vegas are Travis Boak, Matthew Broadbent, Alipate Carlile, Brett Ebert, Hamish Hartlett, Tom Logan, Andrew Moore, Paul Stewart, Jackson Trengove and Justin Westhoff.

Another group of Port players, and McCarthy's girlfriend, Dani, were supposed to meet them in America later this week. That trip has been cancelled.

McCarthy was especially tight with a group of players of his age at Collingwood including Nathan Brown, Ben Reid, Jarryd Blair, Dayne Beams and Lachlan Keeffe.

Nathan Buckley last night tweeted his condolences: ''Thoughts are with family and friends of J-Mac. Infectious personality and perpetual smile will stay with me.''

After four years and 18 games at Collingwood he left the club at the end of last season in search of greater opportunity. He had been an emergency for the grand-final replay, a situation that reflected his career there - close but not close enough to a game in an exceptional side. He left the club without animosity in search of more regular senior games. He found them at Port where he played 21 matches this year

''J-Mac was a great mate to a lot of us. He was a gutsy team-mate and wonderful person,'' Collingwood captain, Nick Maxwell, said.

''Everyone here, especially his closest friends, feel for the McCarthy family. Our thoughts and deepest sympathies are with them as we all bind together during this time. Today we lost a great friend.''

Friends and former teammates Brown, Travis Cloke and Dale Thomas were among the many AFL players to tweet their condolences.

Collingwood players will wear black arm bands on Saturday in their semi-final. So too will members of his Sorrento footy club who play in a grand final this weekend. Eighteen of the 22 members of the team came through the juniors, many of them playing with McCarthy.

AFL chief executive Andrew Demetriou extended sympathies on behalf of the league to the family.

''This is a terrible tragedy for John's loved ones and our deepest sympathies go out to them,'' Mr Demetriou said. He asked people not to speculate on the circumstances of McCarthy's death.

Players from the Essendon Football Club yesterday cancelled a plan to holiday in Las Vegas together later this week out of respect.

Geelong was yesterday among clubs to express their sadness at the news. McCarthy's father, Shane, and brother Matt had both played with the Cats. Matt is currently in Ireland and part of the delay in officially releasing the identity of the player was because it took time to reach him with the news.

The majority of the media chose not to reveal McCarthy's identity until officially released out of respect for the fact family members had not been informed. Some small websites and social media chose to identify him.