Piutau said he had no way of knowing whether or not his All Blacks chances had been harmed by his decision. Coach Steve Hansen has already gone on record as saying he is disappointed.
"I'm not sure, it's out of my hands. All I can do is focus on my performance and I'm going to be playing out of my skin for my Blues team this season," Piutau said.
"I totally can understand I guess the shock that comes with it, but like I said I feel this is the right decision for me and my life moving forward and I'm happy with that."
Piutau said he hadn't spoken to Hansen, but had met assistant coach Ian Foster before and after his decision. Asked how Foster reacted, Piutau said: "I think you would all know."
He added of ruling himself out of the 2016 Olympics sevens team and British and Irish Lions tour of New Zealand in 2017: "I don't think I can find words to express how hard it was."
The money - understood to be about $1million a season - was clearly a big drawcard, but Piutau added: "To me it was to be out of my comfort zone here - more so outside of rugby as well. To experience something new, that was the main factor."
Redman said the Blues wanted him before he left next year but it was New Zealand Rugby's decision to make.
"We'll put our case forward and we've signalled that to them, but we respect the fact that it's their decision in the end," Redman said.
Piutau will play overseas elsewhere before taking up his Ulster contract if he is not able to play for the Blues.