The Kangaroos swooped to secure the 29-year-old midfielder on Monday, capitalising on the Suns' tricky list predicament.
Greenwood was strategically cut by the Suns last week but was expected to be put straight back on the club's list during the draft period.
But David Noble's wife Sarah immediately let the North coach know about Greenwood's shock delisting and potential availability.
As Adelaide's football manager in 2015, Noble was a key person in bringing Greenwood to the AFL after his time playing college basketball.
Noble has left the door open for Greenwood to slot into a leadership role with the rebuilding Kangaroos after offering him a better deal than what he was on at the Suns.
"I was about to jump on a plane to come back to Melbourne and my wife goes 'you better go and have a look on AFL.com, Hugh's been delisted'," Noble told SEN.
"One thing led to another and I reached out on Friday, we got our skates on over the weekend and we were able to secure him as a delisted free agent.Â
"It will be up to players (whether he is in the leadership group)... the players will have an input into that, the coaching staff will have an input.
"Regardless of whether you put him into the leadership group or not, he's still a leader.
"He will still be the same person, he will still have the same direction and he will still want to help people in the same manner, whether has that title or not.
"(Greenwood) came to footy late, so the 29-to-30-year-old aspect didn't worry us and we think his longevity in the game is going to be there."
Greenwood played 32 games for Gold Coast after moving from Adelaide at the end of 2019 - with 51 games for the Crows.
He injured his knee in July and missed the Suns' last six games of the 2021 campaign but is expected to be fit for the start of pre-season training.
Greenwood took to social media after his delisting last week, slamming critics for "clickbait" and said he would be on the Gold Coast in 2022.
But he had to back down on Monday, saying his original post was a "dreadful look".
"If I'm prepared to put myself out there then I've got to be prepared for everything that comes with it," he wrote on Twitter.
"However, from what I've now learnt and what I hope people can understand is that 24 hours can be a very long time in footy.
"I look forward to thanking the Suns in the coming days, but for now we are excited to see what North Melbourne has in store for our family."
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