Blues and New Zealand centre Sonny Bill Williams will be out for six weeks due to a knee injury.
Williams will undergo minor arthroscopy surgery on Friday and is not expected to return until late May.
The 33-year-old did the damage when laying on a try for Otere Black in a Super Rugby clash with the Stormers on March 30.
Williams will be hoping to be back in action for what could be a push for a quarter-final spot.
The rugby league convert faces competition for a place in the All Blacks midfield as he eyes a third Rugby World Cup triumph in Japan.
Blues head coach Leon MacDonald said: "Whatever he decides to do and puts his mind to, he sort of makes happen. If he still wants to keep playing later on he's the sort of guy you would never write off.
"He's a pretty determined guy and this year he really wants to make the World Cup squad and be a part of that. So he's pretty driven to make sure he recovers well from this and gets back on the field."
