Scans have revealed a low-grade MCL injury to Pearce's left knee, ruling the 30-year-old out of next week's clash with Essendon at the MCG.
Fremantle are optimistic the injury isn't serious, but no exact timeline has been set on his return.
"Pleasingly scans have shown it's not a significant injury," Fremantle's general manager of football Joe Brierty said in a statement.
"Early signs are positive and we will continue to reassess Alex's functionality and provide further updates as they come to hand."
Pearce has been in All-Australian form this season, and his injury could open the door for Oscar McDonald to come into the side.
The Dockers made it eight wins on the trot on Thursday night when they kicked the last five goals of the game to turn a 17-point deficit into a pulsating victory.
If Fremantle beat the Bombers next week, they will equal their club-record run of nine wins, set in both 2015 and 2006.
The Dockers further solidified their status as a premiership fancy with the 12.16 (88) to 11.7 (73) win over the Hawks, and the club's fans are set to send the 'Flagmantle' craze into overdrive.
Fremantle coach Justin Longmuir said although the growing hype will be a "distraction", it's a welcome problem for the group.
"I'm happy for our fans to be excited," Longmuir stated.
"We're playing an exciting brand of footy. We've won a lot of games in a row.
"Our fans are starved for success - our fans should be excited about the path we're on.
"But our challenge is to just stay in the moment and give every team our best. It's been a mantra all year and it won't change."
Longmuir believes the growing maturity of his group means they will be able to handle the external noise with a minimum of fuss.Â
One sign of Fremantle's growing maturity is the way they handled their three six-day breaks in a row.
The Dockers beat Carlton, the Western Bulldogs and Hawthorn - all from shortened lead-ins.
"I didn't hear any players whingeing about it, talking about how sore they were. They just got to work," Longmuir said.
"I'm really proud of the group."
Longmuir heaped special praise on Luke Jackson, who tallied nine disposals and three clearances in a monster final quarter.
He also produced an inspirational smother that led to one of Michael Frederick's two late goals.
"He's a bit of a barometer for us, Jacko, when he's up and going and doing his thing on ball," Longmuir said.
"He just adds another layer to our stoppage work. He was huge."
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