All Black flanker Jerome Kaino is in doubt for the British and Irish Lions test series.
He is having knee surgery this week and is expected to be out for six weeks, until just two weeks before the first test against the Lions, on 24 June at Eden Park.
Kaino has been replaced in the Blues starting line up for their match against the ACT Brumbies in Canberra on Sunday night by Akira Ioane.
It is the only change in the forward pack from the last game, a narrow loss to the defending champions the Hurricanes.
Coach Tana Umaga described the loss of Kaino as "a blow" but has confidence in Ioane who has played in all eight games this season, mostly off the bench.
Taranaki and Maori All Black lock Leighton Price, called into the squad this week for the rest of the season as a replacement, will be pressed into immediate action on the bench, with Patrick Tuipulotu, Jimmy Tupou, and Josh Goodhue all ruled out with injury.
All Black prop Ofa Tu'ungafasi will reach his milestone of 50 games for the Blues, when he gets a likely call off the bench this weekend, while newly selected English international, Piers Francis reaches his 20th and blazer game.
Midfielder George Moala is recalled to the starting line-up to form an All Black midfield with Sonny Bill Williams, with Rieko Ioane moving to the left wing.