The Blues have withdrawn Culum Retallick from their squad for the upcoming Super Rugby season.
The veteran lock was expected to miss the majority if not all of the season after rupturing the anterior cruciate ligament in his right knee.
Blues coach Sir John Kirwan says he's a big loss.
"Because he's a big, tall man as you know, but he's also got a lot of experience. So when you start looking around to replace actually that, it's pretty difficult.
"So we're taking a little bit of time with it."
Kirwan says they've got a couple of replacement players in mind and hope to make a decision by the end of the week.
He says they see Patrick Tuipulotu and Liaki Moli has front of the line-out locks as they're hard-workers, but they need a taller lock for the middle of the line-out.
Prop Charlie Faumuina has started training with the Blues, two weeks before the All Blacks are scheduled to return.