The rugby league world is mourning the death of coach of the century Jack Gibson after a two-year battle with Alzheimer's disease and dementia.

The 79-year-old's family said the five-time premiership-winning coach had passed away less two hours before kick-off in Friday night's Centenary Test between Australia and New Zealand at the SCG.

"Jack passed away comfortably today, at 6.32pm at the Garrawarra Centre, Waterfall, surrounded by his family," the legend's family said in a statement.

"We greatly appreciate the wonderful care he had received at Garrawarra, and also the caring and kind support afforded to us, the family.

"We are dealing as well as we can and would ask that Jack's many friends in their sadness that he is no longer with us, do not feel too sorry.

"Jack would not want that; it was his own strong belief and appreciation that he had had a very fortunate life, and we know he would have wanted that to be the spirit of this time."

The wily Gibson earned the nicknamed "Super coach" for revolutionising the role in the 1960s, 70s, and 80s.

Named only last month as coach of the Team of the Century, Gibson won a total of five premierships, guiding Eastern Suburbs to back-to-back grand final triumphs in 1974-75 and then steering Parramatta to a rare hat-trick between 1981-83.

No team since Gibson's classy Eels have won three successive grand finals.

A former Easts, Newtown and Western Suburbs front-rower who played 162 first grade games, Gibson began coaching at the Roosters in 1967, taking the Bondi side that hadn't won a game the previous year to the semi-finals.

His premiership-winning Roosters and Eels teams are regarded as some of the most brilliant club sides ever assembled.

He also coached the NSW State of Origin team in 1989-90.

Apart from his premiership-winning ability, Gibson was also famous for his one-liners as a commentator, his charity work and the coaching techniques he sourced from professional American football clubs.

Parramatta great Peter Sterling, who played halfback for Gibson during the Eels' early `80s dynasty, on Friday night said he was "absolutely shattered" to learn of his former coach's death.

"I played under Jack Gibson for a number of years, won three premierships and I'm absolutely shattered," said the Nine Network commentator.

"I guess we knew this night was coming ... but it's very hard to digest.

"Jack, he loved his players, he cared about his players. And I think the great thing about being coached by Jack Gibson ... is he was more concerned about you off the field than he ever was on (the field).

"He made wonderful footballers, but he also made wonderful people and I thank Jack Gibson eternally for being a part of my life and I know I speak on behalf of every rugby league player and every rugby league supporter who was lucky enough to see Jack in action."

As well as Easts and Parramatta, Gibson also coached first grade football at St George, Newtown, Souths and Cronulla, never spending more than three years at a club at any one time.

"There is no superlative that does justice to his contribution to the game," Australian Rugby League chairman Colin Love said.

"We pass on our deepest sympathies to (wife) Judy and to the Gibson family."

NRL chief executive David Gallop said every player and coach in the game had benefited from Gibson.

"Jack's philosophy was to build the club from the front office to the playing field and to develop men not just footballers," Gallop said.

"He wrote the book for the modern coach and he will be both celebrated and missed."