So who is left?
Tana Umaga would have a strong case but gives the impression he has his life set up as he wants it and could live happily without the stress of being a Super Rugby coach.
Keane has said he'd like to be asked but his name is continually linked with the Chiefs and he was seen in the coach's box alongside Rennie on Friday night.
Super Rugby coaches are jointly appointed by the club and NZRU and, given the importance of the Blues and the need for them to be strong, there is an outside chance of Wayne Smith being asked to take the helm for two years.
Smith has New Zealand's best rugby brain and is a coach many recent All Blacks would rate among the best they have known.
The longer the Blues wait to confirm whether they want a new coach for next year, the less choice they will have. Coaching appointments are a little like school discos — those who sit back and wait find themselves dancing with who is left and not the one they want.
This fate seems increasingly likely for the Blues, who have confirmed their mid-season review has happened but have not yet said — other than he will see out this year — what they have determined in regard to Kirwan.
With just one victory this year, there simply isn't a case to re-appoint Kirwan on merit.
If the decision has been made to make the job contestable at the end of the season, keeping it secret doesn't help the club.
The Blues, despite appearances, are perhaps not the career suicide coaching assignment they appear. No one has had success with them for 12 years but maybe they are on the cusp of revolution. Maybe they just need to find their Vladimir Lenin.
Kirwan's line has been consistent since the losses began to mount - that while the results haven't come, the franchise have made huge progress in improving their talent identification and development programmes. He's made the point that a new state-of-the-art training base is under construction, key players other than Charles Piutau have been retained beyond this year and, possibly against the odds, commercial support for the team remains strong.
A few weeks ago, that progress stacked as a reason to keep Kirwan. Now it merely highlights the one thing the Blues don't have is a man at the helm who can take advantage of all that and build a winning side.
Results suggest the Blues are badly broken but they might not be such a hard team to fix. In Charlie Faumuina, James Parsons, Patrick Tuipulotu, Jerome Kaino and Steven Luatua, there is the basis of a high-quality, competitive pack.
Some recruitment is required in the backline but, again, not as much as it may seem.
As always, they need a world-class No 10, destructive No 12 and one high-quality finisher. Put those into play, and the likes of Bryn Hall, Daniel Bowden, George Moala and Lolagi Visinia may start to blossom.
Further down the pipeline, there are the Ioane brothers and equally promising Blake Gibson and a first XV competition that continues to churn out highly-skilled athletes.
The region has money, a resilient and loyal fan base and one particularly keen and influential backer in the New Zealand Rugby Union.
Making rugby the sport of choice in the wider Auckland region remains a key strategic goal for the national body and, while their focus is primarily on directly engaging the grassroots and community game, no one disputes that it would be helpful to also have an inspirational Super Rugby side to create aspiration.
