YOUNG Essendon defender Aaron Francis will be sidelined for up to five weeks with a calf injury.

Francis, who was selected by the Bombers with pick No.6 in last year's NAB AFL Draft, was sent for scans after experiencing tightness through his calf following training on Tuesday.

The scans revealed a minor tear in his calf and Essendon high performance manager Justin Crow said it was a disappointing setback.

"The sad reality for Aaron is that he'll miss five matches," Crow said.

"We'll make sure that we focus in with his development coach and the rehab team in making sure that he can get the most out of that time and keep improving."

Francis had shown some impressive signs in the Bombers' three VFL practice matches, with his intercept marking and ability to read the play a feature.

Crow said injured ruckman Shaun McKernan had returned to training and could push for selection this week after shaking off an ankle injury.

"Shaun's come up really well from his ankle injury and would have been close to selection last week," Crow said.

"He'll train tomorrow and be looking to put in a good performance on the training track and show us he's ready."

Jason Ashby and Tom Wallis have also resumed full training after being sidelined by injury.

Ashby has recovered from the knee injury he received during the first VFL practice match against Geelong, while a return is on the cards for rookie Wallis after he missed eight weeks with a hamstring injury.

The Bombers have already identified the nine-day break between their clash against Geelong at the MCG on Saturday and the Anzac Day blockbuster against Collingwood as a pivotal period in their season.

"It'll make the world of difference to us," Crow said.

"It means that we can recover up early in the week and then get some really good training in as well. 

"The nine days the following week for the AFL will be a really good opportunity for us to recover, but also get in some good work and set us up for the rest of the year."