Australia are sweating on the fitness of Mitchell Starc after a horror day at Old Trafford left their grip on the Ashes significantly loosened by an all-out English assault.
England went to stumps on day two of the fourth Test at 4-384 and with a lead of 67, after Zak Crawley blasted 189 from 182 balls in a knock for the ages.
Making matters worse for Australia was the fact Starc exited the field late in the day after hurting his left shoulder diving, before an attempted return lasted just three balls.
Australia are hopeful he will be able to bowl on Friday, but with a short turnaround before the fifth Test the situation has the potential to be a concern.
"He's currently got some ice on it and we're pretty confident it will be right tomorrow," assistant coach Dan Vettori said.
"He wanted to get on the field as quickly as possible to see how it was.
"But three balls in a row came to him in the field and he didn’t quite feel comfortable throwing it."
Starc (2-74) had earlier been spotted grabbing at his left hamstring while bowling and looking ginger, but Australia also played down those concerns.
Leading the Ashes 2-0 a fortnight ago, Australia are now at risk of heading to The Oval for next week's series finale at 2-2.
Their only saviour may be rain, which is forecast for the whole of day four, given a draw will be enough to retain the Ashes.
But England's efforts to move the game on quickly after bowling Australia out for 317 now has the hosts aiming to bat only once in the match.
The hosts scored at a rate of 5.34 an over on Thursday, as Crawley and Joe Root plundered the tourists to all corners of Old Trafford.
Crawley's 182-ball knock featured 21 boundaries and three sixes, and by the time he eventually chopped on, trying to pull Cameron Green, England were in complete control.
It came as part of a 178-ball 206-run third-wicket partnership with Root, who was eventually bowled by a Josh Hazlewood ball that stayed at ankle height for 84.
But as well as the pair batted, Australia's showed signs of being rattled by the hosts.
Pat Cummins dropped one catch and completely missed another, while wicketkeeper Alex Carey also put down an extremely tough chance off Crawley's inside edge on 42.
Australia's captain also let two overthrows through in the final session as he failed to back up a Steve Smith throw, in an uncharacteristic show of sloppiness.
While Starc found opener Ben Duckett's edge early in the innings, for one, and snared makeshift No.3 Moeen Ali pulling for 54, Australia's bowling was the worst it has been all series.
They were too straight to Crawley, going away from trying to take his edge outside off stumps with little seam movement on offer.
Their short balls were also often not short enough, allowing Crawley and Root to regularly pull and hook to the gaps in the legside field.
Part-timer turned first-choice spinner Travis Head was called into the attack by the 23rd over and was immediately attacked by Crawley. Head finished with 0-48 off six overs.
Crawley's 93-ball century was the second fastest in all Tests played at Old Trafford, during a particularly damaging middle session where England scored 178 runs in 25 overs.
"In the back of our minds we always knew England had this in them because they play so aggressively," Vettori said.
"It was a pretty flat surface, there wasn't a lot of seam or swing on offer.
"Today was the perfect storm of them coming hard at us, and us not being able to come back against them with wicket-taking options."
