The Brumbies' task against Super 14 rugby champions the Crusaders on Saturday has become less daunting with key All Blacks Richie McCaw, Brad Thorn and Leon MacDonald ruled out.

The trio all failed to recover sufficiently from injuries suffered in their first round home win over the Chiefs last weekend and were omitted from the team named on Thursday for the Canberra Stadium match.

All Blacks captain McCaw received a head knock and team management said the champion openside flanker was not ready to play, although he had improved significantly. He's replaced by George Whitelock.

Lock Thorn (heel) and fullback MacDonald (shoulder) are replaced by Isaac Ross and Stephen Brett respectively with blindside flanker Kieran Read to captain the side.

Crusaders head coach Todd Blackadder said McCaw was close to being available but was not quite 100 per cent.

"He has been following our concussion protocols this week and we've been monitoring him closely but the Crusaders management, along with Richie, have decided that he won't play this week," Blackadder said.

He said it was too early to say how long Thorn and MacDonald would be out for.

Crusaders: Stephen Brett, Jared Payne, Casey Laulala, Tim Bateman, Kade Poki, Colin Slade, Andy Ellis, Thomas Waldrom, George Whitelock, Kieran Read (capt), Ross Filipo, Isaac Ross, Ben Franks, Corey Flynn, Wyatt Crockett. Res: Jason Macdonald, Bronson Murray, Michael Paterson, Nasi Manu, Kahn Fotuali'i, Ryan Crotty, Adam Whitelock.

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