Treacy limped off in the final quarter of Sunday's one-point loss to Essendon at the MCG after his knee collided with an opponent.
Although Treacy was able to return and play out the game, there was speculation that the injury may have been more serious than first thought.
Longmuir put those concerns to rest when he fronted the media on Wednesday, saying Treacy was still a chance to face Geelong at Optus Stadium on Saturday.
"He's got a collision injury," Longmuir said of Treacy, who has kicked 45.15 in a breakout season.
"I think some reports came out that it's significant, but it's not significant.
"He's had scans, but we need a bit more information on it.
"He's going to be touch-and-go for this week.
"He's a little bit sore, but we haven't given up hope this week he's going to be out there."
If Treacy is ruled out, Pat Voss is likely to replace him, with veteran Matt Taberner also a chance.
Longmuir confirmed a sore Sean Darcy will face Geelong despite the ruckman's lacklustre display against Essendon.
Darcy's quiet performance came just a week after he copped some hits to the head and shoulder in a bruising western derby win over West Coast.
"He's not 100 per cent, but he's good to go," Longmuir said.
"We've got a lot of guys who are a little bit sore, a little bit banged up.
"We'll deal with that. He (Darcy) will be right."
Fremantle's midfield unit had an off day against the Bombers, with their performance summed up when Essendon won the last centre clearance to kick the winning point.
The return of Nat Fyfe from suspension will help bolster Fremantle's midfield, and Longmuir is confident his on-ball brigade will bounce back.
Sean Darcy is one of a number of Fremantle players "a bit banged up" but will play against Geelong. (Richard Wainwright/AAP PHOTOS)
"It's a good reminder that we need to play with a proactive mindset," Longmuir said.
"We were a bit reactive. We play our best footy when we're proactive and playing our way and backing ourselves and trusting ourselves."
Fremantle (12-7-1) would have been equal second if they had beaten Essendon.
Instead, they find themselves in sixth spot and in a fierce battle to win back their top-four position.
"We're all disappointed," Longmuir said.
"It's AFL footy, you need to pick yourself up and go again.
"We've been pretty good this year from taking the lessons from wins and losses and moving on to the next opposition.
"We've already done that. We've put that game behind us and taken the lessons."
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