Carlton remain unsure when skipper Marc Murphy will make his AFL return from a ankle injury.

It had been hoped Murphy would only miss two to three weeks when he suffered the injury against Geelong in round 10, but coach Brendon Bolton said on Friday he could be out for another three weeks.

Perhaps of most concern for Blues fans is the coach’s admission that club medical staff still aren’t sure when Murphy is likely to return six weeks after he suffered the injury.

“It’s just one of those syndesmosis ankles that can vary, so it’s really difficult to give an exact timeline on it,” Bolton said.

“We’d love to be able to put an exact timeline on every injury, but with that type of ankle injury you can’t … it just depends how it responds.”

Bolton said no thought has been given to ruling Murphy out for the rest of the season to ensure he achieves a full recovery.

In better news for the Blues, Dennis Armfield appears set to return from a groin injury against Adelaide at the MCG on Sunday, while veteran defender Michael Jamison will return from illness in the VFL.

The high-flying Crows will be aiming for their seventh win in a row, while Carlton are hoping to arrest a three-game losing slide.

The Blues’ misfiring attack has produced an average of just 63 points over the past three games, while Don Pyke’s men lead the AFL in scoring.

“I think it’s not just about match-ups down back – it’s about collective team defence,” Bolton said of his side’s approach to curbing Adelaide’s potent forward line.

“If they get enough supply that’s not pressured they’ll hurt any team.

“We want to score heavily every week. We’ve got some areas that we need to improve in there in terms of some decisions and some execution.