Australia's chances of winning the deciding Test and retaining the Ashes were handed a massive boost by the forced withdrawal of gun England bowler Simon Jones.

As Glenn McGrath moved a step closer to proving he had overcome an elbow injury for Thursday's must-win Test at The Oval, news came through Jones was England's first casualty this series when he was ruled out with a right ankle injury.

The reverse swing specialist, who has taken 18 wickets at 21 and a scalp every 34 balls, was ruled out by England physiotherapist Kirk Russell after an attempt to jog.

England - which retained the same XI for the first four Tests - must now decide what sort of gameplan to pursue in the fifth Test, needing just a draw to win back the Ashes.

Paceman James Anderson would make for a straight swap, while batting allrounder Paul Collingwood would strengthen the order but detract from the bowling.

Australia needs to win the Test to retain the Ashes.

Rain interrupted McGrath's fitness test, but he looked untroubled in his first 15 minutes in the practice nets before the weather forced the Australians indoors.

How McGrath trains and recovers will dictate whether Australia takes five bowlers into the Ashes decider and bats the struggling Adam Gilchrist up the order.

McGrath was confident he had overcome an injured right elbow but must convince team hierarchy he is no longer troubled by a boney growth in his elbow, which kept him out of the fourth Test.

If McGrath, 35, gets through training he should be given the nod to lead a four-man bowling attack likely to also comprise Brett Lee, Shaun Tait and Shane Warne, who will play a crucial role on the spin-friendly south London wicket.

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