Dan Carter decided he needed another rugby fix while locked down during the coronavirus pandemic but said joining the Blues was still "a tough decision".
The New Zealand great has joined the Auckland outfit for the Super Rugby Aotearoa, a domestic alternative to the Super Rugby season that could not be finished due to the COVID-19 crisis.
At the age of 38, three-time World Rugby player of the year Carter admits it will take him some time to get up to speed, but he hopes to make an impact with the team.
He previously played 13 seasons with the Crusaders, before heading overseas for lucrative spells with Racing 92 and Kobelco Steelers, having also had a brief earlier stint at Perpignan.
Carter, the all-time leading points-scorer in international rugby, is relishing teaming up with Blues head coach Leon MacDonald and a new set of players.
He told the Blues website: "Two things from the lockdown that I realised was that I really enjoyed spending more time with my family and that I miss rugby.
"Leon is a good mate and we spoke about me helping out. For me, it is a chance to mentor some young players and to give back to New Zealand Rugby.
"I have not played for several months so it will take me a little bit of time to get game-ready.
"It's an exciting opportunity to train in the same city that my kids go to school in and my family are currently living. It will also be nice to share my experience with some of the young talent they have here at the Blues."
In a separate Instagram note, Carter said he was "back doing what I love".
"When Leon called me with an opportunity to join the Blues squad as a replacement player, it was a tough decision," he added.
The Blues open their Super Rugby Aotearoa campaign against the Hurricanes at Eden Park in Auckland on June 14, and it remains to be seen whether Carter is ready to start that game.
He comes into the squad as a replacement for utility back Stephen Perofeta, who is sidelined with a broken foot.
MacDonald could include Carter in the same team as Beauden Barrett, a two-time world player of the year, but the coach is being cautious.
What is clear is that Carter is unlikely to feature in an accustomed fly-half role, but he could find a place elsewhere within the backs.
"We have two designated 10s in Beauden and Otere [Black], and Dan will be there to help them and our other young backs," MacDonald said.
"If he gets back into playing form that warrants selection, then he could help us as a utility back in midfield or fullback.
"For Dan, it is not about the money. He is here as a favour, with a desire to give back to the sport. We are only a few minutes from his home so it works out perfectly for everyone and we are thrilled."