Farrell injured his left hamstring in Sunday's win against Fremantle which secured the Power second spot and a home final against the Cats on September 5.
The extent of Farrell's injury will be known later Tuesday when the club receives results of scans on the 93-gamer.
But the creative left-footer is long odds to recover in time for the qualifying final in another blow to Port's defensive stocks after the season-ending five-game suspension to halfback Dan Houston.
"As a backline, we've all got to step up," defender Logan Evans told reporters on Tuesday.
"It's not just one person taking a massive step, it's everyone taking a few steps forward and being able to cover the roles all together and as a cohesive group."
Evans earned an AFL Rising Star nomination for his performance against Fremantle when the 18-year-old collected a career-high 23 disposals.
Logan Evans gets set to launch Port into attack with Ollie Wines looking on. (Michael Errey/AAP PHOTOS)
Evans was plucked by the Power in the mid-season draft and has played 10 consecutive games since making his debut in round 16 against the Brisbane Lions.
The backman has trained with Port since January under an SANFL rookie program after being overlooked in last year's national draft.
"It (being overlooked) made me want it more," Evans said.
"I just had to work even harder because I didn't get picked up and it was disappointing but there was no point in putting myself back in my shell ... just step out of my comfort zone and keep doing the work.
"I got to go to Port at the start of the year with the rookie program, so that was a massive step for me, just being in this environment, seeing what it took and then trying to match it.
"Life has just gone pretty quick, it has been a pretty full-on and surreal three or four months."
5°C