The league’s game-day doctor, Colinda Holmes, and intensive-care nurse Rachel 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 said.
«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».
Reflecting on his ordeal on Sunday, Butterfield said «it was touch and go, for a bit».
«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.»
Butterfield said he 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.
Until a few years ago, he was still playing occasional games for the Dudley-Redhead A-grade team he coached.
A sports journalist since 1986 at the Newcastle Herald and Canberra Times (four years), Robert has covered 16 seasons of NRL-level rugby league, three rugby league tours of England, Test matches, Origins, grand finals, international and Sheffield Shield cricket, Wimbledon, A-League soccer and all manner of sport at grassroots level. His stories appear across the Fairfax Media network.