Blues captain and All Blacks flanker Dalton Papalii is expected to miss Saturday's quarter-final with the Highlanders at Eden Park and be sidelined for several weeks due to a medical issue.
The Blues declined to comment when approached, saying the matter was private, but the Herald understands Papalii could miss the remainder of the Super Rugby season and be in doubt for the All Blacks' three-test series against Ireland next month.
Papalii was named to start at openside flanker for the Blues, alongside Akira Ioane and Hoskins Sotutu, against the Highlanders but the medical issue is believed to have since flared up and he is understood to have had key hole surgery.
The 24-year-old has been an inspirational skipper for the Blues this season, leading the team to a record run of 13 unbeaten matches.
The Blues are likely to promote Adrian Choat from the bench as they are already missing Anton Segner following his ankle injury last week.