All-Australian defender Steven May was concussed early in the 38-point upset defeat against Fremantle at the MCG on Saturday.

After being subbed out of the contest, May is also ruled out of next week's clash with Sydney under the AFL's concussion protocols.

Fellow defender Harrison Petty spent extended periods off the ground against the Dockers as he struggled with a knee issue.

Melbourne coach Simon Goodwin was unable to call on versatile tall Tom McDonald after he was a late withdrawal with an ankle injury.

"(May's) a pretty important player to us," Goodwin said.

"To have him out of the game for that period of time, we had to shuffle things around.

"We had Sam halfway through that third quarter going back but the game and momentum had shifted."

Forgotten defender Adam Tomlinson will almost certainly come back into the Demons' team for his first game since round four to play the Swans.

Despite Melbourne's star-studded defence struggling, that is not where the Demons' lost their first game since round 19 last year.

Fremantle obliterated the Dees around the stoppages in the second half, winning the clearances 9-1 in the third quarter.

Goodwin revealed Norm Smith medallist Christian Petracca was ill on Saturday morning, finishing with just 10 possessions.

"That was another concern heading into the game," Goodwin said.

"Clearly to (Petracca's) level he wasn't at his best, he still fought on manfully but woke up a bit crook.

"Hopefully he'll get through that alright in the next 24-48 hours and be fine.

"Clearly he wasn't at his absolute best but there was a reason behind that."

Australian Associated Press