Usman Khawaja insists he will be able to get through the Brisbane Test without pain-killing injections, after being prepared to have an epidural if the series opener had gone to day three in Perth.

Speaking at an Usman Khawaja Foundation fundraiser on Friday, the 38-year-old also revealed how back spasms left him struggling to stand up in the first Ashes Test.

But the opener is confident he will be fit enough to take his place at the Gabba on Thursday, after being retained in Australia's unchanged 14-man squad for the second Test.

Khawaja was unable to open in the first innings last week, because of time spent off the field seeking treatment during England's day-one collapse.

He made a point to field on day two so he could bat in Australia's chase, despite warnings from team medical staff that the injury could get worse.

The opener then succumbed to injury when jumping for a ball that flew over his head at slip, immediately feeling pain in his back on landing.

"Before I went on the physio said, 'Look, you're feeling good now, the slightest movement can make it three, four or 10 times worse, that's the risk'," Khawaja said.

"I was like, I either do that or I don't open for my country. So I went out again, and everything was going fine, until that nick went over my head.

"As I landed, I thought, 'Oh no. Please, you're good, it's just mind over matter'.

"And then every ball I was trying to get down to, it got worse ... I had to call (Alex) Carey over and I was like, 'I can't stand up'.

"I walked off the field, and was pretty devastated."

Khawaja's injury meant he was again unable to open in Australia's chase, with Travis Head taking the chance and hitting a match-winning century.

"I'm really glad that we got it done that night, because the next day I already had the radiology booked," Khawaja said.

"Next day I was going to get an epidural in my back, so I can actually move somewhat.

"It was a tough three days, but I was trying to do everything I could to actually get on the field and play for Australia ... so if the team needed me, I was there."

Head's magical 69-ball hundred has prompted calls for him to open permanently, at Khawaja's expense after a lean run for the left-hander.

Khawaja insisted on Friday he had not paid attention to the talk, after also making clear to AAP ahead of the summer he treated every Test as a bonus after his 2022 recall.

The Queensland opener has a tremendous record at the Gabba, averaging 59.37 there in the Sheffield Shield across the past four summers.

And when it comes to his fitness, Khawaja is confident he will be fine.

He spent one night this week sleeping with a pregnancy pillow, and while that didn't work the veteran said at this stage there was no need for further injections.

"I've never had back spasms before, so it's very new to me," Khawaja said, with his charity helping support children from diverse, rural and low socio-economic backgrounds.

"But the last few days, it's been good."