If there was ever a doubt about Graeme Swann's importance to England, it was erased by the panic that set in when he was struck a painful blow on the bowling arm on Monday.
Swann was later cleared of a broken arm, but for an anxious time before the scans came back, England feared for its match-winning off-spinner.
For all the hype around England's high-class pace attack, Swann is arguably England's most important player against Australia.
He loves bowling to left-handers, and there could be a few of them in Australia's middle order.
Swann, who is England's most successful off spinner with 222 wickets in 52 Tests, would relish the chance to bowl to Phillip Hughes and Usman Khawaja, who have both had problems against spin. So central is Swann to England's Ashes hopes that it is expected dry, turning pitches will be prepared around the country to suit him.
Swann was expected to bowl again in England's warm-up match against Essex to prove his fitness for the Ashes, but has had a disjointed preparation because of elbow surgery and, more recently, back and calf problems.
An injury to England's main spinner would swing the balance of Ashes power towards an Australian team that is starting to get its groove back under new coach Darren Lehmann. Neither of England's back-up spinners can be picked with confidence – Monty Panesar was dropped by Sussex earlier this year and James Tredwell is yet to take a wicket in five county championship matches for Kent.
Australia, at last, has a couple of spin options behind Nathan Lyon, with Ashton Agar's lanky brand of left-arm spin causing excitement and a mature leg-spinner available now that Fawad Ahmed is an Australian citizen.
If all else fails Australia should ensure that hulking Essex fast bowler Tymal Mills, who struck Swann, Tim Bresnan and Joe Root on the arm, jaw and knee respectively, during the Ashes warm-up fixture at Chelmsford, stays around the England camp as a net bowler.