Crusaders openside flanker Richie McCaw could miss the clash against the Blues in Auckland on Friday.
The All Blacks skipper is battling to overcome a calf injury sustained in the 18-10 loss to the Chiefs in Christchurch last weekend.
McCaw did not take part in warm-ups during a Crusaders training session on Monday and the side's coach Tod Blackadder will be wary of pushing McCaw back too soon.
If he is sidelined for the clash with the Blues, McCaw will be replaced by Matt Todd, who impressed alongside McCaw when coming off the replacements bench against the Chiefs.
33-year-old McCaw is not the Crusaders' only injury concern. Centre Ryan Crotty also sat out Monday's training with a similar calf injury to McCaw's.
"There are clouds over a few people who are in contention - Richie is straining a little bit, he has got a little bruise there and Ryan Crotty is not doing a full training today," Crusaders assistant coach Tabai Matson told Fairfax Media.
"We got dinged up, as they [the Chiefs] did, so we are just taking a few days to recover."
Despite the concerns over McCaw and Crotty, the Crusaders were boosted by the news that utility back Colin Slade and number eight Kieran Read are likely to return to action.
Slade should be available if he proves his fitness after recovering from a calf injury and Read confirmed he was available for selection after being rested from the Chiefs match.