PORT Adelaide's Trent McKenzie is not only an unlikely full-back, but an accidental one.

McKenzie, who burst onto the AFL scene a decade ago as a skinny wingman with a booming left boot, says his switch to the key defensive post isn't some sort of master plan.

It just sort of happened.

"To be honest, I am not too sure how it came about," McKenzie told AAP of the positional move which revived his AFL career.

"It was definitely in the SANFL, I was playing as a mid-defender and all of a sudden I have started to play the deepest.

"Obviously there were some big full-forwards I was coming up against and it just evolved from there.

"I ended up playing on the biggest boys."

If someone said a decade ago that he'd become an AFL full-back?

"They'd be pretty crazy," he said.

In 2011, McKenzie was an inaugural Gold Coast player; one of a dozen 17-year-old signings gifted to the new entity, where Ken Hinkley was an assistant coach.

The blond winger was an instant hit: a Rising Star nominee and member of Australia's International Rules squad in his first AFL year.

While the Suns struggled, McKenzie prospered until 2016 and 2017 when cruelled by groin, hamstring and ankle injuries.

He played only seven games in each season and, at the end of 2017, was delisted.

Hinkley, then coach of Port Adelaide, was quick to call.

"I didn't really think twice, to be honest," McKenzie said.

While McKenzie and Hinkley had bonded at Gold Coast, he played just one AFL game in each of his initial two years at Port.

"Thoughts do go through your head, you start to question yourself a little bit," McKenzie said.

Then, somehow in 2019, the switch to full-back coincided with Port reaching the SANFL Grand Final.

"I managed to get myself into a bit of form ... just trying to stay positive was the main thing, even though it was tough," he said.

"You don't want to be playing at reserves level much in your AFL career."

Hinkley took note and entrusted McKenzie with the full-back station in the AFL side for 2020.

The trust was returned.

McKenzie finished fifth in Port's club champion award when the Power were beaten preliminary finalists.

"Ken treats everyone with respect and he gives you honest feedback," he said.

"He trusts you as well. He trusts you can get the job done for him ... that is probably the best thing you can have in a coach, the trust both ways."

Despite his fine 2020 campaign, McKenzie again found himself in the state league in 2021.

Hinkley preferred Tom Clurey, who broke his jaw in round nine and McKenzie was again summoned.

His performances demanded continued selection: 84 per cent disposal efficiency; averaging 5.6 intercept possessions, 5.5 rebound 50s and 6.1 marks - more grabs than Therabody AFL All-Australian full-back Steven May.

McKenzie, at 191cm and 90kg, and his defensive cohorts, including captain Tom Jonas, near-always give up height and weight to opponents.

"We don't speak about it too much but it's definitely a thing," McKenzie said.

"We try to work together as much as we can and if we can get as many two-on-ones as we can, we're in a good spot."

The 138-gamer said the arrival of Aliir Aliir from Sydney - an All-Australian in his first season at Port - had made life easier.

"If I can just hold out my opponent and watch him come over the top, I am doing my job," McKenzie said.

"Just watching him go to work, he deserves everything he's getting at the moment ... he is only still pretty young too so he has got some room for improvement."