Fremantle coach Ross Lyon expects Connor Blakely to miss the remainder of the AFL season and says he will continue to take a cautious approach with Harley Bennell.
Blakely injured his right knee at training on Wednesday and has undergone surgery.
Fremantle initially expected the meniscus damage would sideline him for six weeks but Lyon now expects the figure to balloon after the surgeon ended up repairing the cartilage instead of just trimming it.
Fremantle are unlikely to play finals, meaning Blakely won't play again barring a remarkable recovery.
"The operation went well," Lyon said.
"They were able to repair it, which is really significant for his future because cartilage plays a significant (role in) cushioning.
"So he'll be in better shape as he gets older but it will mean a longer rehab. He will be really stretching it to get back (this year)."
Lyon hopes to see Bennell make his AFL return this year but only after an uninterrupted block of WAFL games.
Bennell has been plagued by calf issues since crossing to Fremantle at the end of 2015 and suffered another scare while playing WAFL on June 2.
It was a false alarm and he will line up for his sixth WAFL game of the season on Saturday.
However Lyon won't hand Bennell a senior call-up until he's confident the midfielder's body can handle the rigours.
As it stands, he estimates he's about two-thirds of the way there in terms of volume and sprints.
Bennell's three-year contract expires at the end of this season and the club is leaning towards re-signing him.
"Harley just needs to keep building," Lyon said.
"It's not about the next six weeks, we want it to be about the next six years.
"We think that if we can build the body and the form, we know he's a top-flight player and he would add nicely to what we're doing."
Fremantle (6-7) are aiming for three wins on the trot against Brisbane at Optus Stadium on Sunday.
The Dockers have been bolstered by the return of Michael Walters (suspension) and Alex Pearce (broken thumb).
Blakely and Ryan Nyhuis (axed) drop out.
Brisbane hard-nut Mitch Robinson returns from a broken toe, while Daniel McStay and Jake Barrett also come in.
Star defender Harris Andrews will miss with concussion, while Sam Mayes and Zac Bailey were dropped.