Carlton skipper Marc Murphy is still three weeks away from an AFL return, with his ankle injury healing slower than expected.

Murphy strained ligaments in his right ankle early in the Blues' Round 10 upset win over Geelong and it was initially hoped he would miss two to three weeks.

But the Club has confirmed Murphy will miss another three games, which would put him the frame to return in Round 18 against the Sydney Swans at ANZ Stadium.

"Murph's still out with his ankle ... he's progressing ok – a little bit slow – but he's still another three weeks away before he's ready to go," Blues' Head of Football Andrew McKay told Carlton Media.

Carlton will also be without Dennis Armfield for another two weeks as he recovers from surgery to repair a ruptured testicle.

The Blues take on Collingwood on Saturday night and will be looking for their first clean sweep of the Pies since the 2012 season.

In-form defender Sam Docherty said his teammates had studied their round-seven win over Collingwood, but added that Nathan Buckley's side were a different proposition now.

Magpies spearhead Travis Cloke didn't play in that game and Docherty admitted he was unsure if he would line up for the Pies at the MCG.

"You plan for both ... it is a bit of a mystery whether he plays or whether they go for a bit of a different mix," Docherty said.

"We've just got to plan for all outcomes and as it gets closer we'll really nut down to who's playing and how we can defeat them."