The Ashes: Clarke faces crucial net session

Australia vice-captain Michael Clarke will have a final net session at the Gabba on Wednesday in a bid to prove his fitness for Thursday's first Ashes test.

Clarke is nursing a back injury but showed by batting without any major discomfort on Tuesday that he appears to be on track to prove his fitness, meaning standby player Usman Khawaja's test debut will have to wait.

"Everyone saw him in the nets, he seemed to get through it fine, and he was in good spirits when he got through it," Australia opener Shane Watson said on Tuesday.

"That is a very good sign."

Australia's Mitchell Johnson tested out his new Ashes game plan on his team-mates on Tuesday, bowling short-pitched deliveries so nasty that Ricky Ponting was lucky to escape without injury.

Australia's all-time leading runscorer needed all his defensive skills to fend off a savage bouncer from the left-armer which reared off a good length and threatened to slam into the skipper's throat.

Johnson, who is keen to target England opener Andrew Strauss with a few well-placed bouncers, took his Ashes preparations up a notch as he focused on specific strategies following some video analysis.

"We looked through a bit of footage again today," Johnson said on Tuesday.

"I was trying to bowl the length I want to bowl, particularly to their top order.

"Every batter that came in today, I was thinking of English batters. So when Shane (Watson) came in today I was thinking of a (Kevin) Pietersen sort of type.

"I'm really raring to go, to get out there and to bowl fast and really be aggressive out there."

- AAP