He then lined up in the circle against long-time rival Tom Walsh at the Sir Graeme Douglas International Track Challenge at Auckland's Trusts Stadium on Thursday night.
All eyes were understandably on world champion Walsh, although he was upstaged by Poland's Konrad Bukowiecki. In the subplot to that contest, Gill said barely a word as he secured third with 20.76m, just 8cm behind Walsh.
"He's a pretty humble guy. He's not going to be the one all bolshy," said Hellier.
It's an attitude she believes has helped Gill in the past 15 months.
"There were times when he would have had different thoughts going through his head. But you know what? I'm immensely proud of how he's then stepped back up.
"It's not an easy thing to say to someone 'you can't do any physical activity, even though it's what you've done your whole life and you have to be careful with everything you do for the next few months.' And then to add to that, he ended up tearing his pec. We just wondered when he'd catch a break," Hellier said.
"But he's dealt with it all so well. Really maturely. And he's been so receptive to change. Which is such a hard thing to do. Because why would you want to change something that you're so good at already?"
The change has been in areas for which Gill is well known. He became associated with his YouTube videos, where he would lift massive weights, the country marvelling at this teenage behemoth. Gone are those days.
"You're taking a big, strong guy who can bench press 247kg to now a guy who can't do that. But we are finding other ways for him to improve."
Hellier's also had to change how she coaches him.
"It doesn't change from a technical perspective because the fundamentals are still same. But you're dealing with a different athlete. He can now move differently. We are focused on speed. The fitter you are, the quicker your recovery rates, and you just function on a different level. It's allowed us to achieve things quicker.
"It's a cool game trying to find the perfect frame and perfect athlete."
Hellier has noticed Gill seems almost at peace.
"That's what happens when you deal with a life-threatening illness. But he doesn't usually get riled up anyway. It's not in his nature."
As for what he does in the circle, Gill and Hellier are determined to hit 21m on a regular basis.
"He did it tonight [Thursday]. It wasn't in competition but he did it tonight in training. I'm very, very confident he will."
