Australia could have stumbled on a new formula for their T20 World Cup defence, with Ashton Agar opening the batting against Sri Lanka in Canberra.

As Australia continue searching for the perfect formula to defend their T20 World Cup crown they found an interesting solution on Tuesday night in the form of Ashton Agar.

Almost nine years on from his historic 98 on Test debut against England batting at No.11, Agar's batting journey came full circle at Manuka Oval when he opened the batting against Sri Lanka as the hosts wrapped up the five-game series by taking a 3-0 lead.

The left-arm orthodox spinner didn't set the world on fire in his 13 runs off 13 balls, outside of blasting Maheesh Theekshana for six over deep mid-wicket, but should he nail down a top-order batting spot, the 28-year-old will unlock a series of options for Australia.

Most notably, it means they could play three genuine spinners with Adam Zampa and Glenn Maxwell T20 regulars.

Agar said opening the batting was a pre-planned experiment, having been told it was likely should he break into the team.

"That to me was really exciting and it was received with great excitement as well," he said.

"I had good chats ... the main messages really were to not over complicate things.

"If you move around too much, particularly if the ball is starting to move around, that's when you find yourself in trouble.

"And when the ball is up, I guess trusting your swing as much as you can."

Agar is no mug with the bat; he boasts three first-class centuries and average about 28, leading to some speculation he could even slot into Australia's Test side as a spin option for the upcoming Pakistan and Sri Lanka tours.

Either way, Agar said his confidence and belief was back, particularly compared with how he felt before his most recent Test series against Bangladesh in 2017.

"I remember being at the ground ... I could feel that anxious feeling that you get before a game, particularly because I hadn't played a Test in a long time," he said,

"But I sort of had to remind myself I'd played against teams who were just as good as that Bangladesh batting line-up, and I played in front of much bigger crowds and with full confidence.

"You just have to remind yourself that you put on your Australian helmet ... that's the only thing that really changes and I guess it's that you have to foster and practice that belief."