Sinfield went on to play rugby union for Yorkshire Carnegie for a season subsequently, and has now been appointed as an RFL director.
“I was very close to staying on,” he told BBC Sport.
“I would have loved to have finished the NRL season, but I decided I’ve had my time.”
Sinfield has now started his two-day-a-week job at the RFL, and inists that he will be professional and honest in his task of assessing various aspects of the game during his tenure.
“I’m not here to be popular, although I’d quite like to be popular,” he said.
“I’m here to make the right calls at the right time. It’s too easy to throw mud at the RFL and Super League. It’s everybody’s role to make our game better.”