Segner appeared on the Nelson schools scene when MacDonald was coaching Tasman.
"I heard a lot about him, it was more about his leadership and drive," he said.
"When I was coaching Tasman, we would get some schoolboys to come down, and they were doing like work experience.
"He stole three or four balls at our training run, and it was getting some of the older players were getting a bit frustrated with him, so they were tempted to take him out.
"It just showed at a young age that he was a determined, tough fighter. He loved the physicality. To his detriment he has had a few setbacks with injuries that you get as a young seven.
"Because of his diligence, he's built his frame now and is an impressive 106-107kgs.
"He's got everything we're looking for in terms of the types of players we want, aspirationally. We want guys who want to be All Blacks because that means they're willing to do a little bit extra than the normal person," he said.
The leadership quality was not necessarily related to captaincy but personal management.
"He has that in spades. You can rely on players like that to deliver consistently. We're really fortunate to have him with us."
Lock Sam Darry, who made his first appearances for the side last year before some head knocks ended his season early, had similar drive.
But forwards coach Tom Coventry said he was expecting him to continue to grow in 2022.
"We've had an eye on Sam's development for a while. We knew it was going to take more than just last year to get what we wanted out of him.
"He's very similar to Anton in that he's driven to be an All Black. He's a hard worker, he does his homework well, he's a great fellow.
"He's a young man, he's only going to get better," he said.
Having Luke Romano on hand would be good for his development. They were expecting big things out of him.