The All Australian centre-half back has failed to overcome a foot injury, with Crows coach Neil Craig unwilling to chance Bock in their crucial home clash against the Magpies.

Collingwood are perched in fourth position on the ladder, a win clear of the fifth-placed Crows.

Adelaide's ambitions of pinching a top four spot, and associated double chance in the finals, will be ended by a loss in the sold-out match at AAMI Stadium on Saturday night.

With such high stakes, Craig said he was not prepared to risk Bock, who has fluid on a foot.

"Nathan was too sore to train today without a needle, so we decided not to play him," Craig told reporters in Adelaide on Friday.

"When you're playing with needles and training with needles, the sorer the area gets.

"There might be a point where we have to say to Nathan `we're just going to have to go with this [injury], and he'll be okay with that - but were not at that point at the moment."

Craig also revealed talented winger David McKay, despite being named in Adelaide's squad, won't make his comeback from a two-week absence with a hamstring strain.

Craig and his Collingwood counterpart Mick Malthouse both expect a tight, intense encounter.

"Massive test," Malthouse told reporters in Melbourne on Friday when quizzed about the finals-shaping fixture.

"They (Adelaide) are playing some very good football, it's round 19, everything's very much alive in the competition, so it's always a testing time.

"We've always had some close encounters against Adelaide, their structure is very sound, Neil Craig is a bloke I admire as a coach, he gets the best out of his team, they're highly disciplined.

"You'd like to have an easy one .... (but) Adelaide just don't give you any breathing space, so we're not going to have an easy game."

Collingwood dropped rookies Jaxson Barham and Steele Sidebottom, recalling Chris Dawes and Brad Dick.