The Dockers had 24 of the 25-man squad named for the Richmond clash fly to Melbourne, but Ross Lyon said Sandilands has been given another night in Perth to overcome various ailments.
"Aaron Sandilands is in doubt. He’ll fly out tomorrow, hopefully, so we’re taking all of our emergencies across," Lyon said at Perth airport.
"He’s been a bit off.
"Cold winter, bit of a sniffle, bit sore. We’ll monitor him and we're really optimistic, but we’re prepared if he doesn’t play."
If Sandilands were to miss, it would be another significant blow to the Dockers ahead of their first trip to the MCG this year.
Fremantle is already missing Luke McPharlin, Hayden Ballantyne and Matthew Pavlich due to injury and suspension, and losing Sandilands would make Sunday's important clash even tougher.
"We'll certainly miss them," Lyon said.
"Pav and Hayden have kicked a number of goals over the last few weeks.
"It's a dent, but we're a professional sporting organisation that's paid to get the job done without them.
"It's going to be a big challenge but we're going to work really hard.
"I think if we stand for anything, if you want to lift the lid on anything, it's our work rate and our determination not to give up."
Lyon said there was no doubt over Clancee Pearce, who suffered a heavy concussion in last Sunday's 28-point win over West Coast.
"He feels pretty good about it and we feel good about it," Lyon said.
"We know that Clancee’s welfare is number one, but we’re keen for him to play as well, so he’s all clear."
Paul Duffield is set return after two weeks on the sidelines with a calf injury.
"He trained fully today and cleared everything, so he’s really confident as well," Lyon said.
"He’s an experienced player capable of some really high level performance, so we’re really thrilled to have him back."
Despite the quality missing from Fremantle’s forward line and defence, Lyon felt that the Tigers midfield posed the biggest threat.
"Their stoppages with (Ivan) Maric and their midfield is going to be a real challenge for us," Lyon said.
"They got us last time there. Hopefully we've learnt some lessons and we'll be much improved."
