After initially being named in the defending champions' starting lineup last night, McCaw was ruled out this morning in a significant setback to their chances.
McCaw suffered a blow to the forehead during the 13-10 defeat of the Sharks in Durban two weeks ago which had required stitches. He received a another knock below the eye during last weekend's surprise 13-20 loss to the Cheetahs.
Coach Todd Blackadder said McCaw's removal was precautionary.
"We wanted to wait to see how he was at training and beforehand Richie said he was feeling okay," Blackadder told Radio Sport this morning.
"But at the training he said he was not feeling 100 per cent, so we have decided to rule him out." McCaw has had ongoing problems with concussion throughout his career. He was ruled out of the second-round match against the Brumbies in February because of a head knock.
Tasman's Jonathon Poff will get his first start in the number seven jersey.
Blackadder has reinstated flanker Kieran Read - who will captain the side - lock Isaac Ross, halfback Andy Ellis and fullback Leon MacDonald for the Lions match after they were on the reserve bench for the Cheetahs encounter.
Tighthead prop Owen Franks retains his spot ahead of Bronson Murray.
Blackadder has also handed the kicking duties to MacDonald ahead of first five Stephen Brett and Colin Slade.
The Crusaders, currently eighth in the standings, need big wins from their remaining three round-robin games against the Lions, Reds and Blues to keep alive hopes of retaining their title.
