Dockers defender Brennan Cox has had his pre-season interrupted, with the 25-year-old set to be sidelined for a month with a diagnosed stress fracture in his fibula.

The ever-reliable stopper left the training track at Cockburn last Friday complaining of leg soreness before being sent for scans on Monday as his teammates conducted match simulation.

While Cox won't be taking part in any on-feet portions of his pre-season program, Fremantle confirmed in a club statement that the recently recommitted defender will work off-feet in order to be fit for Round 1.

"While it's an unfortunate interruption to Brennan's pre-season on the track, he will be able to continue cross-training during this off-legs window to maintain his conditioning before returning to football,” Fremantle GM of Football Joe Brierty told Dockers Media.

“Brennan has the full support of our medical team to ensure that this setback can be managed appropriately and have him at full strength for the opening round.”

Cox signed a six-year extension to remain in purple and white last September, with the South Australian set to call Fremantle home until the cessation of the 2030 season.

The Woodville-West Torrens product has laced the boots on 102 occasions, debuting during Round 17 of the 2017 season

Fremantle will commence its 2024 season when it plays host to Brisbane at Optus Stadium on Sunday, March 17.