Petrie helped the Eagles seal an unlikely finals birth on Sunday evening, as they defeated the top-placed Crows by 29 points to secure an eighth place finish.
Coach Adam Simpson confirmed the new post-match.
“I might have jumped the gun a tiny bit there, but he was indicating he was looking at retiring,” Simpson said.
“I did ask him before I spoke on the ground if he’d like to thank the fans.
“I think he’s been really embraced by our supporters and members and I think they know him for who he is as a person as well – to do that in 12 months is a credit to him and his family.”
Petrie last year became the oldest ever player selected in the Rookie Draft, at 34 years and two months old.