Both the Dockers and Lions, who were in the middle of Lachie Neale's appeals board hearing when teams were due, named unchanged line-ups for Saturday's decider at the MCG.
Neale then sensationally had his one-match striking suspension overturned on Thursday evening, meaning Brisbane won't have any changes.
Cox hasn't played since injuring his calf in the final-round loss to Carlton on August 22, with knee soreness keeping him out for two matches a month earlier.
But the defender was held out of last week's WAFL grand final to get through a match-like session to remain in contention for Saturday's game.
Journeyman key back McDonald has filled in admirably in Cox's absence, and has been named despite copping a heavy knock from teammate Mason Cox in Fremantle's thrilling preliminary final win over Sydney.
Both players trained on Wednesday before the Dockers arrived in Melbourne on Thursday afternoon.
The Dockers then opted to stick with McDonald, with Cox, veteran Jaeger O'Meara and Chris Scerri named emergencies.
Earlier, Fremantle defender Jordan Clark said he would be hurting for the player who missed out.
"It's one of those things where you just wrap your arms around him," Clark said.
"It's pretty cliched, there's always a heartbreak story and unfortunately it's got to happen every year.
"However it falls, we just wrap our arms around whoever it is and they're still part of us."
Changes to Brisbane's line-up had always appeared unlikely if Neale was cleared to play.
Answerth, who had recovered from an ankle injury, appeared firmly in contention to replace Neale but is instead an emergency along with Bruce Reville and Cody Curtin.
Rain is expected on Saturday, which could yet play a role closer to the game in terms of any late changes.
But Clark didn't have any concerns about the weather.
"It wouldn't affect us too much," the 25-year-old said.Â
"It's a game of footy, goalposts at each end, the same for both teams."
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