Barnett will next week face the toughest possible initiation to Origin football, as only the fourth Blues player this century to debut in a decider at Suncorp Stadium.
A member of Maguire's squad for the first two camps, the Blues coach revealed on Monday it had been Barnett's training ethic that had helped earn him a spot.
Part of that commitment, Barnett revealed, included missing the birth of his second son Zane in Auckland to be with the Blues.
Picked as a reserve for game one, Barnett and his wife Clare opted for him to stay in Australia training with NSW teammates in their first two full sessions in late May.
Only after training did he make his way to the airport, knowing by then he would miss Zane's birth.
The 30-year-old returned to Australia after his wife and Zane were out of hospital, and he was back in time to finalise preparations for the series opener.
"It was just a decision my wife and I made and an opportunity I couldn't pass up," Barnett said.
"It was a great moment for me, and it will make for a cool story one day with the family. It was a cool moment."
The forward hopes Zane will be able to join his family in Brisbane for next Wednesday's decider.
Barnett considers himself a far different man to the one who last lived in Australia in 2022 while playing with Newcastle.
Banned for six matches early in that season for reckless and dangerous contact, the Taree junior has made a point of maturing after opting to sign with the Warriors.
"It's been about a three-year process for me, maturing," Barnett said.
"I just realised along the way, natural progression in life. I have people who believe in me at the Warriors, and that really helps.
"My wife, my mum and all of my family (have helped). I had to work a little bit on myself. Having a coach (in Andrew Webster) who believes in me helps as well.
"(CEO) Cam George at the Warriors has been amazing. They have tidied a few things up just to get me to where I am."
On the field, Barnett has changed too.
He has gone from a back-rower to prop, and has been one of the Warriors' most consistent players this year.
That versatility was the other key factor in his selection for the Blues in place of Haumole Olakau'atu, with NSW wanting to roll through Queensland in the middle.
"I have a good knowledge and understanding of both roles," Barnett said.
"I was naturally a back-rower as a junior. Since I have gone to the Warriors (I have) moved to the front row.
"I think I am naturally more of a front-rower, especially in today's game with it being a bit faster."
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