Farrell has been withdrawn from the Power side to host ladder-leaders Fremantle on Adelaide Oval on Saturday.
And coach Josh Carr says the 27-year-old may not feature again this season.
"Not sure what it will look like for the rest of the year, but at this stage it's probably unlikely that he will play again," Carr told reporters on Friday.
"We have been chasing our tail a bit with it. Where we sit right now (15th on the ladder), we'll give him the time to try and get it right."
Farrell is the latest struck down in a horror stretch of injuries - 13 players are on Port's injury list including captain Connor Rozee (hamstring), vice-captain Zak Butters (ankle) and star forward Mitch Georgiades (concussion).
Key on-baller Jason Horne-Francis will also miss the Dockers game because of suspension.
Butters, who is weighing massive offers from Victorian clubs to leave Port, still holds hope of playing again for Port despite his injury.
"We know what Zak is like, he's going to be doing everything he can to get back," Carr said.
"He's up against it, there's no doubt about it."
Despite the raft of players unavailable, Carr was pragmatic.
"It's footy. It's contact sport - it happens," he said.
"There is so much opportunity for us, whether that's individually or as a group.
"We're not here to make up the numbers for this weekend.
"We're here to win games of footy, that is clear to us every week: if we get certain areas right in our game, then we give ourselves the chance to walk away with a win."
Pre-season signing Balyn O'Brien, a 19-year-old defender, will make his AFL debut against the Dockers with Carr comparing him to Port's former captain Tom Jonas.
"He's a farmer so he goes and gets his hands and knees dirty, and we love the way he plays footy," Carr said.
"We love the contest he provides and never-give-up attitude."
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