Matson was one of the main pillars in Kirwan's plan presented to the board recently in what was effectively a job application, and now that his preferred assistant isn't coming, Kirwan is likely to be casting around for suitable alternatives.
The most recent name linked to Kirwan is Wayne Smith. It is understood that Kirwan and the board are very keen on Smith and a partnership of sorts is apparently possible, but not on a formal basis.
It is understood that Smith, who will rejoin the All Blacks this year as a defensive coach, is willing to help his good friend next year after his contract expires in January.
Smith's analytical skills and ability to relate to players would be a huge asset to the franchise, but he is more likely to be involved as a mentor to Kirwan, who has admitted he has deficiencies in areas such as recruiting and selection but that he is willing to improve.
The Blues board and chief executive Michael Redman yesterday maintained their silence on a process unravelling by the day, but the Crusaders were happy to take the moral high-ground, their chief executive Hamish Riach saying their approach to Matson had created an "intolerable" distraction at a crucial time of the season.
Todd Blackadder's team are ninth on the table, but only three points behind the Bulls, who are currently in the lowest playoff position.
"The Crusaders have been lucky on two fronts in my view," Riach said. "One, that Tabs has been so open internally, so there's been no side-swiping or surprise for us. And secondly, we've been very lucky it's been bye week because this sort of distraction is just intolerable in a team environment and we've been able to get through that while the boys aren't here."
Matson, who confirmed he would remain at the Crusaders until at least the end of 2016 when his contract expires, is believed to have visited the Blues this week, but refused to confirm or deny it.
"I won't delve into the detail but I have had initial conversations with the Blues and today really is about stopping the speculation," he said. "I'm having no further conversations and I'm really committed to finishing the campaign ..."
The Crusaders can switch their focus back to rugby, but for the Blues, that isn't likely to happen for a while yet.