Fremantle has reportedly been monitoring Longmuir as a potential replacement for Lyon, which is now likely to gain traction after the axing of Lyon on Tuesday.
Longmuir currently sits in his second year at the Pies and holds a contract for 2020, however, clubs have recently shown a commitment to allow assistants to pursue senior jobs when available.
The 38-year-old is a former teammate of Fremantle’s head of football in Peter Bell and is said to have strong support from the board.
The sacking of Lyon and CEO Steve Rosich now sees Peter Bell as Fremantle’s chief decision-maker.
Other candidates for Fremantle’s top job include current assistant coaches David Hale and Peter Sumich.