ENGLAND fast bowler Andrew Caddick will know on Wednesday if he is fit enough to face Australia in the third Ashes Test.

Caddick underwent a scan on his injured back today after sustaining a back spasm during the second Test, in which he batted at number 11 as England slumped to an innings-and-51-runs defeat at the Adelaide Oval.

He failed to improve this morning and a scan revealed "wear and tear" on his back.

Caddick will have a steroid injection into his back tomorrow, with a fitness test scheduled for Wednesday.

England physio Kirk Russell said: "The scan has revealed long-standing wear and tear consistent with a fast bowler of Andrew's age which is continuing to cause him pain.

"He will have a steroid injection into his back in Perth tomorrow and his fitness will be reassessed at nets on Adelaide. At this stage he has not been ruled out of the third Test."

The tourists at least have cover in Alex Tudor and Chris Silverwood if Caddick fails to make a recovery and they have called Durham all-rounder Paul Collingwood into the squad as insurance against doubts over Michael Vaughan and John Crawley.

Vaughan is still sore after being struck on his right shoulder by a Jason Gillespie bouncer during the Test, while Crawley is failing to make the progress they had hoped after sustaining a slight tear to his thigh against Australia A in Hobart last week.

Collingwood, who has been playing grade cricket in Melbourne, has been a regular member of England's one-day squad for the last 18 months but has yet to feature in a Test and will meet up with the squad in Perth tomorrow.

"He's been called up as cover for one Test and we'll make a decision after that," said Fletcher. "He's been playing in Melbourne so there shouldn't be a problem with acclimatisation or jet leg."

England have also put Worcestershire off-spinner Gareth Batty on stand-by for the squad, although he had to pass a fitness test on his injured shoulder first.

But he will stay with the Academy in Adelaide and only travel if the tourists decide they need two spinners.

Most of the remaining fit members of the squad had a short, optional practice at the Adelaide Oval nets this morning with only Marcus Trescothick, Craig White, Mark Butcher and Richard Dawson missing out while injured trio Caddick, Crawley and Vaughan had a session with physio Russell in the hotel pool.

"After what has happened the players are probably going to be mentally down and when you're like that you're going to probably practice bad habits," added Fletcher.

"Everybody is mentally down when you lose a Test match just as you are mentally up when you win and it's up to us to lift ourselves in the next few days before the next Test.

"We just have to focus on this next Test and we have to make sure we go out there and win it - if we do that then we're still in the ball game."