FREMANTLE skipper Alex Pearce has escaped serious injury but has been ruled out for up to a month in a setback for the Dockers.

Pearce landed awkwardly on his left forearm in a marking contest against Gold Coast on Sunday, with scans revealing a fractured forearm that will sideline the 29-year-old for 3-4 weeks.

Pearce has been in All-Australian form this season and has arguably been the best-performed key defender in the League, shutting down the opposition's best tall forward each week.

His form has made up for the loss of Brennan Cox (hamstring) and Oscar McDonald (knee) in round one, with inexperienced backman Josh Draper stepping in before Hugh Davies was called up for his debut against the Suns.

The Dockers are unlikely to rush the return of Cox, with the 25-year-old playing managed minutes for Peel Thunder's reserves team on Saturday in his first match on the comeback trail from a serious hamstring injury.

McDonald remains around two months away from returning after undergoing knee surgery in early April for a complicated injury that included damage to his posterior lateral corner.

Fremantle will this week face Sydney, which boasts a three-pronged tall forward line that includes Joel Amartey, Logan McDonald and Hayden McLean.

Options for coach Justin Longmuir would include playing Luke Ryan as a key defender, as he has done well in the past when required, and using the 193cm Heath Chapman as a third tall defender. 

"Obviously, disappointing to lose Alex for the next few weeks, he has had a fantastic year down back to date and his leadership has been second to none," Fremantle executive general manager of football Joe Brierty said.

"Our performance health team will work closely with Alex to return to football as soon as possible and provide him with the best support possible following his surgery.

"With Alex unavailable it provides an opportunity for someone to fill that role."