Nathan Lyon admits he was "absolutely filthy" with being dropped from the second Ashes Test, even as chief selector George Bailey insists his axing is a "one-off".

The 38-year-old offspinner was not on the team sheet for the second Test at the Gabba, with seamer Michael Neser preferred in an all-pace attack.

It marks only the second time since Lyon's Test debut in 2011 that he has been overlooked for a home Test, and the first time since 2012.

The news came after Lyon was used sparingly in the Ashes series opener and was also overlooked for the day-night Test on the tour of the West Indies this year.

But that did not make it any easier for the veteran to process.

"(I was) absolutely filthy," Lyon said on Channel 7 of his axing.

"But I can't do anything about, so I'm just trying to make sure I can play my role in making sure I can get the guys ready."

Lyon only learned of the selectors' decision to go in with an all-pace attack at 12.30pm (local time), an hour before the toss for the day-night match.

As of 8.30pm local time, Lyon had not brought himself to speak with Bailey or coach Andrew McDonald about his omission.

"I haven't really sat down with 'Ronny' (McDonald) or George yet. When things settle down in my own head (I will),' he said.

"I'm not the first player to miss a Test match and I won't be the last, but obviously I'm pretty gutted, because I know the role that I can play within Australian cricket, especially at a venue like this.

"I'm extremely disappointed, but I'll do whatever to make sure these guys (the Australian team) are right."

To compound his forgettable day, Lyon was struck on the ankle while bowling to teammate Beau Webster in the nets during the lunch break.

He was seen in discomfort, but the Australian camp confirmed there were no injury concerns.

Lyon had played 71 home Tests in a row before being left out.

Australia's chairman of selectors Bailey revealed Lyon's displeasure after Josh Inglis and Neser were chosen ahead of Webster and Lyon.

"I don't think he agreed with it and that's fine," Bailey said.

"I think Beau Webster is in the same boat, that (omission) was heavily debated.

"Nath will disagree with the decision and that's perfectly OK. I think he disagreed with the decision in Jamaica.

"There's no qualms about players feeling like they can impact the game."

When Lyon was omitted for the third and final Test in the West Indies this year, national selector Tony Dodemaide also said it was "a one-off".

Bailey was emphatic about Lyon playing the third Ashes Test.

"Very much it's a one-Test decision. Nath will play in Adelaide," Bailey said.

"It's just how you think you're going to structure up the resources and how it's going to be used when it gets dark, when you think you're going to be using seam bowlers, how many bowlers get used in a day, when you think the new ball is going to be available, that sort of stuff."

Bailey said the decision for Pat Cummins not to play was made on Wednesday night, with the captain still troubled by his back injury.

Like Lyon, he is expected to return for the third Test in Adelaide, which begins on December 17.

"He could've played, but there would've been some restrictions around the overs," Bailey said.