FREMANTLE ruckman Aaron Sandilands won't return for up to six weeks after his recovery time from broken ribs and a collapsed lung was pushed out.

Sandilands had been closing in on his return after surgery in April, but he could now be sidelined beyond the Dockers' round 15 bye after advice to extend his time in recovery.  

He has been listed on the club's injury list as a 4-6 week proposition.

• The injury list: Your club's sidelined players

"Aaron saw the surgeon this past week and she's asked for his recovery to go for a bit longer to allow the bones to heal a bit better," Fremantle sports science manager Jason Weber said on the club's website.

"At this stage he’ll be another couple of weeks."

Key defender Alex Silvagni also appears to have suffered a setback in his recovery from the calf injury that has sidelined him for the past three weeks. 

He is now expected to be sidelined for between four and six matches, according to the Dockers. 

Meanwhile, young key defender Alex Pearce underwent successful surgery on his broken tibia bone on Sunday.

"Alex's surgery has gone really well," Weber said.

"He's at home resting and we look forward to getting him back into training in the capacity he can within the next week or two."

Stephen Hill (adductor) and captain David Mundy (calf) could be available for Saturday's clash against St Kilda after training on Tuesday.

Anthony Morabito (hamstring) will need to prove his fitness at Thursday's training session to return, while Shane Yarran will be unavailable because of calf soreness.