NARRM has been dealt a blow ahead of its top-four battle against Fremantle with premiership forward Tom McDonald ruled out. 

The key tall is battling an ankle injury and wasn't able to complete training on Friday morning. 

Sam Weideman comes into the side with the club hopeful McDonald will be available for next week's clash against Sydney. 

"Tom has some ankle soreness, which meant he wasn’t able to get through our final training session this morning," GM of AFL football performance Alan Richardson said.

"We will monitor Tom over the next few days, but at this stage, we’re hopeful he will be available next week."

It means the Demons will have three changes from last week's win over North Melbourne with Jack Viney and Toby Bedford in the 22 in place of injured winger Ed Langdon and omitted midfielder Luke Dunstan.

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McDonald has been in hot form with seven goals in the past fortnight after an indifferent start to the year that including a week in the VFL. 

The injury opens the door for Weideman to have another chance to impress after kicking nine goals in his five AFL games this season.

The Demons are yet to taste defeat this year, but could face a stern test against the fourth-placed Dockers, who are coming off back-to-back losses.