MELBOURNE defender Tom McDonald is set to be missing from the Demons' side for Sunday's encounter with the Western Bulldogs at Etihad Stadium.

McDonald struggled to get through training on Friday morning and AFL.com.au understands he is dealing with a right calf injury, which required scans. 

Luke Tapscott has replaced McDonald in the 25-man squad.

With James Frawley playing forward, McDonald has been the Demons' No. 1 defender this year and has handled the difficult tasks well.

McDonald's absence may force the Demons to rejig their line-up and push Frawley into the backline.

Alex Georgiou, who played the first seven games of the season as a key defender, may also come into the mix after training with the club's main team on Friday morning.

Bulldogs forward Jarrad Grant has also been withdrawn from his team's squad for Sunday.

Grant copped a nasty hit to his nose last Saturday against Port Adelaide and has failed to recover in time to face Melbourne. His place in the 25-man squad has been taken by Fletcher Roberts.

Adelaide has withdrawn David MacKay from their Showdown squad to face the Power on Sunday with Mitch Grigg taking his place. MacKay suffered concussion in last week's loss to Essendon and failed a fitness test on Friday morning.

Full teams will be named on Friday evening.