The 19-year-old was over halfway into his first AFL season when it became apparent he had bulked up too much for his height of 184cm. 

He was also feeling sluggish and finding it hard to run around after eating what he thought was a normal breakfast, including toast. 

So the Saints' dietician suggested he forego foods containing wheat for 10 days – and the results were almost immediate. 

"I dropped two or three kilos in about three weeks and I was back down to what they wanted me to be at for my playing weight," Dunstan told AFL.com.au. 

"I feel absolutely better. I was having toast for breakfast every morning and it was all sitting in my stomach and I couldn't run around as well, and I was feeling heavy too.

"I definitely feel better now I've sorted it out."

It took some adjusting. Dunstan initially added rice to his list of banned foods that already included carb-heavy bread and pasta, before realising the grain was actually beneficial to his energy levels.

"I was a little bit flat to start with, but once you get used to it your body adapts," he said.

 

"Rice is fine and I have that with chicken so it isn't too bad.

"I still get my energy and I felt a lot better after just 10 days so I've been sticking with it and I feel lots better."

Just before his intolerance was discovered, Dunstan suffered his first big injury when he tore the labrum in his shoulder.  

Then, against Fremantle in round 18, he further injured it when he chipped a bone in the joint. 

He managed one more game before – despite his protests – he was sent in for season-ending surgery. 

For Dunstan, the worst part about being shuffled into hospital was the fact he wasn't part of his mentor Lenny Hayes' final few games. 

"I tried to argue with the coaches a little bit but I ended up losing that battle," he said. 

"It was disappointing, but obviously they want to get me right for pre-season so I can have a big year next year."

Dunstan was asked to attend the Saints' final round game, against the Crows at Adelaide Oval, and wasn't sure why he was instructed to wear his club polo. 

It became apparent after the game when Hayes made an emotional presentation to the first-year midfielder, after choosing Dunstan to wear his famed No.7 guernsey in 2015. 

"It was a pretty special moment," Dunstan recalled. 

"I was very lucky and for him to pass the number on now, I feel like I've got a pretty big role to play and he's left me and trusted me to do that, so I want to repay him.

"It's a massive honour and hopefully I can fill the big shoes he's left for me."

While Hayes won't go into coaching, Dunstan expects to stay in touch with the club legend as his own career progresses. 

He also expects to have nearly a full pre-season – he will be in the rehabilitation group for six weeks before Christmas and will join the rest of the players after that. 

Dunstan recently signed a contract extension that will keep him a Saint until at least the end of 2017.