LONDON: Australia fast bowler Brett Lee faces a race against time to be fit for next week's third Ashes Test against England.

A side injury has forced Lee to miss the first two Tests and the Australians have suffered in his absence, losing the second Test at Lord's to go 1-0 down in the series.

The 32-year-old needs to play in the tour match against Northamptonshire, starting on Friday, to prove his fitness for the Edgbaston Test and a decision on his involvement is expected in the next 48 hours.

Australia coach Tim Nielsen knows his side's attack at Lord's lacked a pace spearhead, with left-arm quick Mitchell Johnson struggling while taking a mere three wickets for 200 runs in the match.

But he fears rushing Lee back too soon would only increase the chances of another injury lay-off.

"We will see how we go. We are progressing him," Nielsen said. "The positive thing is that in a tour game we do have the flexibility on how much we can bowl him or how much we don't bowl him.

"He hasn't bowled yet, so we just have to sit with the medical staff over the next few days and chat: about how much we need to get into him and whether it is going to progress him to the stage where he could play in the third Test.

"My feeling is, if it is not going to mean he is available to play in the third Test match, we are going to have to be really careful about rushing him back."

Lee has not played for Australia in a Test since the Boxing Day defeat to South Africa.

He displayed his credentials for a return with six first-innings wickets against England Lions last month but suffered discomfort in his ribs as a by-product.

Nielsen confirmed: "The injury that he has is a bowling-specific injury and history shows if you have those injuries again it tends to be six, eight, 10 weeks before they come right, if you actually re-tear the side.

"Two, three, four overs in the nets is probably not enough to prove that he is right to go.

"If he had to bowl say 11 overs in a row, like Andrew Flintoff did at Lord's, to win a Test match for us, we would want to be comfortable that he is strong and fit enough and able to do it."

Johnson starred with the bat at Lord's but had a miserable match in his primary role as a pace bowler where he seemed to have little to fall back on when the usual accuracy generated from his low-slung action deserted him out in the middle.

The 27-year-old has been working with ex-England bowling coach Troy Cooley but Nielsen said talk of dropping Johnson for the third Test was way off-beam.

"Most importantly we need to keep things in perspective," said Nielsen. "He's had a brilliant two years, he's done nothing but improve in every Test since then, we're not hiding from the fact that he didn't have a brilliant Test here, but he got better as the Test went on, which was pleasing.

"He's been too good for us to think 'oh, he's not going to play at Edgbaston'."

Stuart Clark, the leading wicket-taker in Australia's 5-0 Ashes rout of England in 2006/07, is waiting in the wings should the tourists decide they need to make a change to their pace attack.