The 34-year-old sustained a fibular fracture just above his left ankle in the first week of December when a pedal smashed into his leg.

Mundy took part in pre-season training for two weeks after the incident but reported soreness on Friday and was sent for scans that uncovered the fracture.

The club is unsure how long the midfielder will be sidelined, but he requires non weight-bearing immobilisation for at least four weeks.

"Most likely, the fracture is a result of an injury that David sustained whilst riding his bike with his children," Fremantle football chief Peter Bell said.

"... David is a professional and we are sure he will do everything he can to get his body in the best shape for 2020.

"Given the type of injury, at this stage there are no set time frames for David's return to football."

Given that uncertainty, Mundy is in doubt for the Dockers' season-opener against Essendon at Marvel Stadium on Saturday, March 21.

Mundy has displayed impressive durability throughout his career, playing 316 games in 15 seasons since making his debut in 2005.

But he joins a host of AFL players to have suffered unusual pre-season injuries.

Adelaide champion Nigel Smart famously suffered badly burned feet walking across hot coals in a motivational exercise gone wrong at a pre-season camp.

Ex-Geelong ruckman Brad Ottens once impaled himself on a garden stake, former Western Bulldogs forward Jarrad Grant was sliced by a stingray in Port Phillip Bay and St Kilda's Dan Hannebery broke his foot on his sister's uneven backyard steps.

Mundy had been due to front a press conference on Wednesday, but teammate Stephen Hill replaced him.

"It's obviously disappointing and pretty hard for David but he's in good spirits," Hill said.

"He'll get around the boys, he's a professional, and get back as soon as possible."

Hill has endured a wretched two years with soft-tissue injuries restricting him to just 16 games, but the 29-year-old reported he is enjoying a strong pre-season and has suffered no setbacks

Australian Associated Press