Nathan Lyon has been Australia's sole tweaker in home Tests for the vast majority of his career, barring a handful of games when he was snubbed or joined in the attack by a fellow spinner.
Lyon is expected to be ruled out of Friday's fourth Test at the MCG, after tearing his hamstring fielding a ball during Australia's 82-run win on Sunday.
The 38-year-old ended the day on crutches, using them to hobble across Adelaide Oval as Australia left the venue with the Ashes urn wrapped up.
Pat Cummins is also set to miss the Melbourne Test as medical staff manage his return from a back injury, with the captain also a chance to sit out Sydney with the Ashes secure.
Steve Smith will almost certainly return to Australia's batting line-up and captain the team, after overcoming vertigo and returning to the nets in Adelaide.
Travis Head led celebrations on Sunday night but the squad will quickly shift focus to pursuing a 5-0 series win amid a short turnaround before Boxing Day.
Day one of the fourth Test is already sold out. There will be an increased police presence at the match, including officers with semi-automatic rifles.
"We know it's unusual to see police with these weapons outside the MCG but I want to assure everyone this is about greater safety and providing reassurance to the community," Victoria Police Chief Commissioner Mike Bush said.
On the field, Lyon's void shapes as a significant change for Australia.
Lyon was left out at both the WACA in 2012 against India and earlier this month at the Gabba, but on both occasions that was for Australia to go with four quicks.
Otherwise Australia have not entered a home Test without him since 2011, when Michael Beer was the last player other than Lyon to be picked as a frontline spinner.
West Australian Corey Rocchiccioli is every chance of debuting, after being the form spinner of the Sheffield Shield this season.
Matt Kuhnemann has impressed in five Tests, but part of his value in selectors' eyes is an ability to bowl in tandem with Lyon and turn the ball the other way.
Todd Murphy is another option, having most recently played for Australia in February in Sri Lanka.
Spinner Cooper Connolly also played on that tour as an allrounder, while legspinner Mitchell Swepson has not played a Test since the 2022 Sri Lanka tour.
"Gaz (Lyon) is pretty close to irreplaceable. The ability to take breakthroughs but also control innings is really important," Cummins said.
"So, it's going to be hard to replace, but we've got some guys who have already had a taste of international cricket around the traps.
"Other guys have done really well in domestic cricket. It's been one of the benefits, of the Sri Lankan tours, even West Indies, where we take a couple of spinners.
"There's guys that can step in and you feel like it's not going to be too overwhelming for them."
Cummins, meanwhile, has indicated he will take the conservative approach and could sit out Melbourne and Sydney after an aggressive return from injury allowed him to play in Adelaide.
Mitchell Starc and Scott Boland have both bowled close to 70 overs across the past two Tests, but would both likely be keen to play in Melbourne.
Brendan Doggett, Michael Neser and Jhye Richardson wait in the wings as bowlers, while selectors will likely decide whether Usman Khawaja or Josh Inglis makes way for Steve Smith.
AUSTRALIA'S OPTIONS TO REPLACE NATHAN LYON:
* Matt Kuhnemann. Left-arm orthodox. Tests: 5, 25 wickets at average of 22.20. Sheffield Shield form this season: 4 wickets at 36.
* Todd Murphy: Right-arm offspin. Tests: 7, 22 wickets at 28.13. Shield form: 10 wickets at 23.70.
* Corey Rocchiccioli. Right-arm offspin. Tests: Nil. Shield form: 20 wickets at 28.20.
* Mitchell Swepson. Right-arm legspin. Tests: 4, 10 wickets at 45.80. Shield form: 21 wickets at 36.04.
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