FREMANTLE cannot afford to underestimate a depleted Sydney Swans outfit, defender Garrick Ibbotson says.

The Swans have been dealt a huge blow in the lead-up to Saturday's qualifying final at Domain Stadium, with star forward Lance Franklin ruled out due to a mental health issue.

Important midfielders Kieren Jack (knee) and Luke Parker (ankle), and defender Nick Smith (hamstring) have already been ruled out of the clash.

Franklin proved the difference between the two sides in last year's qualifying final at ANZ Stadium, when he kicked two goals in three minutes at the start of the last quarter to swing the game in the Swans' favour.

But Ibbotson said the Swans were still dangerous even without Franklin.

"He's a good player," Ibbotson said on Tuesday.

"He did play a good game in the final last year.

"We know that our philosophy is 'if one goes out, another one comes in and plays a role'. They will be thinking the same, and if we're not on our game we will get easily beaten.

"They will have guys who are sort of champing at the bit to get into the team.

"That is something we speak about a lot. Names don't mean anything when we come to play a game of footy. We know that whoever is going to be on the park is going to be a formidable opponent for us, and we have to prepare the best way we can to play our best footy to get the job done."

Match preview: Dockers v Swans

Ibbotson said he didn't know if he would play in defence against the Swans, having spend the past two weeks up forward as coach Ross Lyon has experimented in search of the right attacking mix.

"I was probably as surprised as anyone," Ibbotson said.

"I didn't really know until late in the week (against Melbourne in round 22) and Ross said they wanted to try me forward as an option.

"I spent a bit of time at training and watching Pav (Matthew Pavlich) and watching a bit of their footage along the way to try to learn as much as I can.

"I haven't played there a whole lot, but I have enjoyed it."

Ibbotson said he had not even played forward in his junior career but added the experience would help him as a defender.

"I can empathise with a forward now about the delivery from a midfielder or a backman," Ibbotson said.

"(I know) if it goes over your head how hard it is. So as a backman I probably need to improve that a little bit now. I can see how hard it is when the delivery is not there."

Ibbotson and teammate Stephen Hill will both play their 150th games on Saturday, and both were named in the All Australian 40-man squad for the first time on Tuesday.

Fremantle midfielders Nat Fyfe, David Mundy and Lachie Neale were also nominated.

It is Neale's first nomination, while Mundy was named in the 40-man squad in 2010 and 2013 but has never made the final 22.

Fyfe was nominated in 2011 and 2013 and was selected in the side for the first time last year.