MELBOURNE defender Oscar McDonald is almost certain to miss his side's clash against Essendon on Saturday with an ankle injury, opening the door for veteran Lynden Dunn to return to the team.

McDonald was on crutches on Monday after rolling his ankle against Greater Western Sydney in the opening round, and coach Paul Roos said the young backman was doubtful to take his place in the side.

Roos said the Demons would pick a healthy team above all else, although he noted that Dunn, Angus Brayshaw and Heritier Lumumba would all come into the selection mix.

"We made a really conscious decision to pick a fit and healthy team (against GWS), and as it turned out it was a probably a good decision," Roos said on Wednesday morning.

"Dunny had that groin strain early in the (NAB Challenge) game against the Bulldogs (on March 6) and he missed the following week, so as much as anything it was based on the fitness side of things.

"Now we look at the opposition team … they're not super tall the Bombers. (Joe) Daniher's up there and a lot of small/ mediums. That’s probably the only impediment to a big getting in the team."

Brayshaw, who injured the medial ligament in his knee against Port Adelaide in the club's first NAB Challenge match on February 27, and Lumumba, who had surgery on both of his ankles at the end of last season, will be assessed on whether they have had adequate preparations.

"The discussion is going to be around the fitness side of things again. H (Lumumba) only came back to training five or six weeks ago. He's a really experienced player," Roos said.

"At the moment we're healthy, but those guys will certainly come into consideration. It becomes more about health and touch and [whether] we feel like this week's too early or not."

But the Demons are going to stick to the timeline set for Christian Petracca, who made a promising return to football in last week's VFL intra-club match.

Melbourne is playing it safe with Christian Petracca. Picture: AFL Media

Petracca looked a class above the rest in the hour-long scratch match at Gosch's Paddock on Good Friday, and Roos said a decision on whether he would play in Saturday's VFL practice match against Box Hill at Casey Fields would be made later on Wednesday.

The plan is for the highly-rated youngster to play a month of VFL football before being considered for senior selection, after a year out of the game because of a torn anterior cruciate ligament.

"Fitness is a big thing. We know he's talented and can do some pretty special things, which we saw before he did his knee," Roos said.

"With [the interchange cap set at 90] now, there's nowhere to hide on an AFL ground.

"The plan will stay the same and when we think he's at a suitable level of fitness we start to judge him on his form, and what round he gets into the team will be determined by those two factors."

Roos also indicated NAB AFL Rising Star nominee Clayton Oliver is likely to be given a spell at some stage throughout the season, despite an impressive 22-disposal effort against the Giants.

"You learn from your young guys every year. Last year we probably ran Angus (Brayshaw) into the ground a little bit.

"But those young guys you look to rest. There was a game last year where Gussy had the flu and we probably should've pulled him out.

"We learn from that. I certainly wouldn't think [Oliver] will play all games this year."