ADAM Tomlinson will be called up to cover Steven May's absence in defence as Melbourne considers making half a dozen changes for this week's clash with Sydney.

The Demons, who had a 17-match winning streak ended by Fremantle last week, host the Swans at the MCG on Saturday night.

Key defender May will miss through concussion but gun midfielder Christian Petracca is back to full health after battling the flu.

Versatile tall Tom McDonald has overcome an ankle injury and is one of a handful of possible inclusions but won't be sent to the backline.

Melbourne coach Simon Goodwin confirmed Tomlinson will play his first match since round four as a direct replacement for May.

"(Tomlinson has produced) six weeks of outstanding VFL footy," Goodwin said.

"He's back winning one-on-one contests and he's playing our defensive system to a really high level.

"Obviously with May, (Harrison) Petty and (Jake) Lever it's been really hard to get him back into the team, but the opportunity has arisen and he deserves his spot."

As with McDonald, Christian Salem (ankle), James Harmes (hamstring), Ed Langdon (ribs) and Michael Hibberd (calf) are also in the mix to return from injuries against Sydney.

Goodwin dismissed suggestions that bringing back up to five or six players at once could destabilise the team.

"All our guys that will be available for selection know our system incredibly well and one thing we know that works well for our team is cohesion," Goodwin said.

"Those guys know their role incredibly well and have built cohesion over a long period of time.

"It doesn't faze me one bit the number of guys that come back into the team; it will just be whether they're fit, healthy and ready to perform."

Premiership star Salem has not played at any level since round one, when he was an early casualty in a win over the Western Bulldogs.

The 26-year-old ball-winner could yet return through the reserves, with the Casey Demons to host Sydney in a VFL curtain-raiser at the MCG before Saturday night's AFL clash.

Teams will be named on Thursday night.

"Christian's done a power of work," Goodwin said.

"He's had a long campaign in rehab and one thing I do know from our high performance staff is they have been able to rehab players incredibly well.

"We'll have a look at Christian at training and make sure he's ready to go."

After Melbourne's clash with Fremantle it was revealed Petracca was ill on the morning of the game, with the Norm Smith medallist having just 10 disposals in the Demons' first loss of the year.

Petracca wasn't at the club on Monday but has since returned and was due to take part in Melbourne's main training session on Wednesday.

"He's brought a bit of energy and spirit back to the group, which has been fantastic," Goodwin said.

"He's fine, he's ready to go.

"He had a small dose of the flu but got through that no worries, pulled up really well and he's ready to train fully today.

"I know from Christian's perspective he's looking to get back into some main training and really set his week up for a really important game for us."

Petracca made the call to play against Fremantle despite his illness and Goodwin said he will continue to support his players and medical staff on such matters.

"You back the assessment of your medical team and your athlete and in this situation we supported Christian playing," Goodwin said.

"He was keen to play, he didn't perform to his normal level, but that doesn't mean he didn't have an impact either."