Former Australia opener Justin Langer says the loss of Kevin Pietersen could be the crucial factor in deciding the fate of the Ashes this summer.
Langer believes that England losing their star batsman could have the same effect Glenn McGrath's absence had on Australia during the epic 2005 series.
Pietersen has been ruled out after an Achilles operation, and Langer feels he was England's biggest threat despite his limited impact in the series because of injury.
The Somerset skipper can recall how McGrath inspired Australia to victory in the first Test four years ago, but then suffered a freak injury when he trod on a ball during practice before the game at Edgbaston.
England took advantage of his absence to level the series and then won at Trent Bridge to triumph 2-1.
"The Pietersen injury is a huge blow for England - not unlike the Glenn McGrath injury during the 2005 series," said Langer.
"It was at that point where the momentum of the series changed and, after losing the second Test, it was like swimming into a tidal wave.
"We were then up against an England side growing in confidence and momentum plus all the expectations of the English public. It was really hard work after that.
"It could be the same now with Kevin Pietersen. He has not made a lot of runs in this series but Australia know that he and (Andrew) Flintoff are the two dangermen.
"I think Australia will take some confidence from Pietersen not being there for the rest of the series and, on the flip side, England will know it is a big loss."
Langer believes Ricky Ponting's men can emulate England in 2005 and come from behind in the series, despite having a less experienced outfit than four years ago.
"Australia have got a big job ahead of them," he said. "There is no doubt about that but they can definitely come back.
"This is a much more inexperienced Australian side and it will take good leadership from (Ricky) Ponting and the management to make sure they stay relaxed and focused.
"But, if they can do that, there is no reason why they can't level the series or even win it."