A highly popular figure in his four years with Collingwood, John left for Port Adelaide at the end of last season but remained a close friend to many at the Westpac Centre.
“This tragic news has come as a shock to everyone at the Collingwood Football Club”, President Eddie McGuire said.
“John was an exceptional young man in the prime of his life with the whole world ahead of him.
“We are devastated to hear of his passing, and our hearts go out to his loving parents Shane and Catherine, his family and friends.
“We are proud that John wore the black and white jumper and his contribution to our club will never be forgotten.”
In his honour, Collingwood’s players will wear black armbands in their first semi-final encounter with West Coast at the MCG on Saturday night.
“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.
“It’s a terrible day, a devastating day. 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.”
Only 22 years of age, John played 18 games with Collingwood after being recruited from the Dandenong Stingrays with pick 31 in the 2007 national draft.
He got close to premiership success in 2010, when named as an emergency for the grand final replay of that year, and played 11 matches in his final season with the Magpies before seeking a regular senior opportunity at Alberton.
John played 21 matches this year with Port, for a career total of 39 across five seasons.
