Bairstow is on standby to deputise for Matt Prior in next week's first Test, just as he has in their final warm-up match against an Australian Invitational XI at the SCG.
Prior's torn calf means England may have to leave it until the eve of the Ashes opener in Brisbane before they can decide whether he has recovered in time to keep wicket and bat at number seven.
If not, Bairstow will be their man in both pivotal positions.
Over the past three days in Sydney, the Yorkshireman believes he has proved his readiness - to himself at least - and if the call comes, memories of his spectacular one-day international debut will spur him on.
It was as a 21-year-old, back in September 2011, that Bairstow turned England's ODI against India on its head with a blistering man-of-the-match 41 not out from 21 balls.
England are unlikely to need that sort of tempo on this assignment.
But Bairstow is confident he has the mettle to produce what is required, should his chance come again to add to his 12 Tests to date.
Asked how he is handling the nervous wait, after England had closed day three against the Invitationals with their hosts 153 for four and only 39 runs in front, he said: "That's professional sport ... the nature of the beast.
"It's something you can prepare yourself for over the years that you come through - not just junior cricket, senior cricket.
"I only found out the day before I was going to make my one-day international debut down at Cardiff.
"It's something that has happened before - and if it was to happen again, then so be it."
Bairstow contributed 48 runs to England's cause here, shared a stand of 106 with Joe Root (75) in a first-innings 418 all out - and has so far taken four catches.
He concedes he still has work to do on his wicketkeeping.
"It's still in progress," he said.
"But I feel good after the performance of the last couple of days - it's filled me with confidence.
"If the opportunity does come along (next week) I do feel I'd do a decent job."
He was able to reassure England's supporters that Root is none the worse for a blow on his little finger while batting, and that - as far as he knows - Prior's condition is improving too.
"Everyone is hoping that Matt is fit, for English cricket.
"Who wouldn't want Matt Prior to be fit and taking the stage at the Gabba for that first Test?
"But if that isn't the case then it's an opportunity (for me) to go out there and play for your country.
"As far as we know ... from the medical team, he's feeling good at the moment.
"He's as chirpy as ever ... progressing as they are hoping."
England had to work hard to take four Invitationals wickets, and stay in with a good chance of victory.
Aaron Finch (59) had been in poor form recently, but gave England's seamers plenty to think about with an early assault - and although he was then out trying to hit Graeme Swann for a second successive six, he gave an indication perhaps of the treatment the off-spinner can expect this winter.
"I think we saw towards the end of the Ashes last time, they tried to attack him quite early - and had a bit of success doing that," Finch said of Australia's Test batsmen.
"I suppose when you let a quality, world-class spinner just settle in ... and just keep bowling, the chances are he's going to get a wicket eventually.
"So if you can get on the front foot to him, and try and attack him early and put him under a bit of pressure, it can help guys through the middle order.
"We've got very, very good players of spin - 'Pup', Smithy, 'Watto' and 'Bails' now - all very, very good.
"If that's part of the gameplan - I'm not sure it is - being attacking and free-flowing against someone like that can't be a bad thing.
"I think that's the way these guys play, and have had a lot of success doing that.
"Knowing 'Boof' [Australia coach Darren Lehmann], for the right-handers especially, it will be a bit of a gameplan."
England's bowlers struggled until late in the day, but Finch was impressed by what he saw latterly from Steven Finn - especially the delivery which clean-bowled Callum Ferguson.
"It's obviously not ideal conditions for the fast bowlers, with the (sandy) run-ups.
"It can make it quite tough.
"I thought his spell with the old ball was outstanding - reverse-swing - and I think the ball that knocked 'Fergie' over was probably ball of the day."
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