Essendon coach John Worsfold is unsure when Dyson Heppell will be cleared to return to the Bombers' AFL line-up as the skipper continues to struggle with a sore foot.
Heppell was a late withdrawal from the side that defeated Sydney at the MCG last week and appears a doubtful starter against North Melbourne on Saturday.
The 27-year-old was restricted to testing his sore left foot in light, short-range kicking drills on the sideline while his teammates were put through their paces in Wednesday's main training session
In a concerning development, Worsfold revealed there is an element of doubt over how the issue will progress, with surgery a possibility down the track.
"It's one of those things that you don't know how it's going to respond," Worsfold said.
"He's had it for a few weeks and it's been pretty good, but we came off a couple of games at Marvel Stadium and Optus Stadium - grounds that are talked about as being a little bit harder.
"Hopefully he'll be able to manage it all the way through.
"It's a genetic thing. I won't go into it too much because I don't really understand it, but it's basically something that he had in his other foot that he had fixed years ago.
"This one may or may not need some (surgical) intervention at some point or it may just be all right."
Heppell has previously had a pin inserted in his right foot to stabilise an unfused growth plate.
Worsfold told reporters that defenders Michael Hurley (hip) and Cale Hooker (back) would both be fit to take on the resurgent Roos at Marvel Stadium.
Zac Clarke managed just one possession to three-quarter time in the win over Sydney, but Worsfold appears set to stick with the former Docker, who will have his work cut out against Todd Goldstein.
"All we can ask is for Zac is to play his role for the team and give a good contest," Worsfold said.
"It wasn't surprising that his best quarter was the last quarter ... he started to get into the groove of the game.
"I'm confident that he'll be able to improve with more game time and give us a good contest."
Essendon will wear the logo of charity partner Challenge, which provides support services for children with cancer and their families, in the Tackling Childhood Cancer game.
Australian Associated Press