The 53-year-old played alongside a host of former Knights teammates, including Mark Sargent, Matt Gidley and Mark Hughes, in a golden oldies curtain-raiser before the Newcastle Rugby League All Stars game at No.2 Sportsground.

After a rousing post-match rendition of the team song, he collapsed in the dressing room in front of shocked teammates. He stopped breathing and required CPR before being rushed to hospital by ambulance. 

The Newcastle RL's game-day doctor, Colinda Holmes, and intensive-care nurse Rachael Paton were credited with keeping Butterfield alive until paramedics arrived.

Ms Paton was at the game as a spectator because her partner, Daniel Abraham, was playing for the opposition team, the Newcastle RL Old Boys.

"Basically Tony was having a heart attack in the dressing room and Colinda, who was the sports doctor on site, provided some basic first aid," Ms Paton recalled.

"We stayed with him until the ambulance arrived, and fortunately they brought a defibrillator with them. 

"While he was waiting to be transported to hospital, he went into a cardiac arrest.

"So we were able to start CPR and defribillate him really quickly, which I think was an excellent outcome."

Ms Paton said that for intensive-care medicos and paramedics, dealing with life-threatening situations was "our bread and butter".

Butterfield said on Sunday "it was touch and go, for a bit" and was extremely grateful for the treatment he received. "You're just amazed how they slot into professional mode and know what to do, and get the job done," he said. "It was fortuitous for me that they were on hand."

Butterfield said doctors had since inserted a stent and cleared the blockage, which they described as "a third the size of a pea".

One of eight members of Newcastle's Hall of Fame, Butterfield is a former club captain who appeared in 229 top-grade games, including the 1997 grand final victory.

Since retiring from rugby league at the end of the 2000 season, Butterfield has forged a successful business career and written a popular weekly column in the Newcastle Herald.

Until a few years ago, he was still playing occasional games for the Dudley-Redhead A-grade team he coached.

"It was stinking hot but I felt fine until after the game, when I had a cold shower," he said. "Then I started feeling weird."