A Perth radio personality believes he's been given the inside scoop on the future of Brownlow medallist Nat Fyfe, which doesn't bode well for Fremantle fans.

Brad Fitzgerald, co-host of the 'Carmen & Fitzi' show on Western Australian radio station 96FM, says Fyfe will accept a multi-million dollar deal with St Kilda, and will move to the Saints at the end of the season.

“The offer is worth $1.5 million a season and it is - as far as legally wise - it’s virtually accepted,” Fitzgerald said on Monday morning.

“He can’t sign yet but it’s basically a done deal and he is going to St Kilda.”

Fitzgerald said the news was given to him by a St Kilda executive, but wouldn't reveal the identity of the culprit.

“I can’t name names but this has come from a high-ranking board member of St Kilda,” he said.

Fyfe was named Fremantle's captain at the beginning of the 2017 AFL season, and has averaged 26.8 disposals over the opening six rounds. He is out of contract at the end of the season.

The club is yet to comment on the issue.