Ibbotson and Luke McPharlin were forced out of the Dockers' side to face Greater Western Sydney on Sunday at Patersons Stadium with calf injuries. 

The Dockers expect McPharlin to return next week to face St Kilda, but Ibbotson's prognosis isn't as positive.

Although McPharlin's injury has been described by Fremantle as relatively minor, he did tear his calf in round 15 last season and missed eight weeks before returning for the Dockers' finals series. 

The veteran defender has already missed five games this year with two separate injuries. He missed rounds eight and nine with a quad issue, and then missed three weeks with a medial ligament strain. 

Ibbotson has also had a wretched run with injury in the past two seasons. 

He missed last year's finals series after requiring Achilles surgery, and after returning for his first game of this season in round three against Hawthorn, he dislocated his shoulder in the first quarter and missed a further six matches. 

Fremantle forward Chris Mayne was unconcerned by the latest injuries to McPharlin and Ibbotson, believing both players will recover quickly. 

"Those boys are really diligent with their recovery and rehab and we expect nothing less," Mayne said. 

"They will be focusing on getting themselves right and trying to get back in the side. 

"It is becoming tough for positions and that's what we love, every player is really fighting to get themselves a seat on the bus."

The Dockers don't lose any experience this week, as skipper Matthew Pavlich and All Australian defender Michael Johnson come in as replacements. 

 

Mayne said the competition for spots is fierce at Fremantle. Matt de Boer still can't find his way into the line-up after two matches in the WAFL, and Michael Walters' return from ankle surgery could be as close as a fortnight away.

"It's excellent to see that we have got a lot of players fighting for positions," Mayne said. 

"It keeps you on your toes and it keeps you hungry. 

"You don't want to give your spot up to anyone because you never know how long you could be out for. It's an exciting time for us."

Mayne has endured his own injury struggles this year. A back injury hampered him throughout the pre-season, and he has kicked just eight goals in 14 matches this season compared to 39 and 37 respectively in the last two years. 

"I missed a fair bit of the pre-season," Mayne said. 

"But I've been able to work well with the physios and fitness staff on getting myself right, and I feel great at the moment. I feel like I'm running out games better and I'm able to probably have a bit more output."