Australia opening batsman Justin Langer has a 50 percent chance of playing in Sunday's second Test against Pakistan after injuring his back, team physiotherapist Errol Alcott said on Thursday.

Langer was hurt while bending to pick up a ball during practice at the Melbourne Cricket Ground on Thursday. A scan revealed a bulging disc.

He had "very severe back pain", Alcott told reporters, adding: "It's 50 percent he might play, 50 percent he might not play. But it's just a bit too early (to say) at this stage.

"He's in bed and not feeling very good."

Langer is Test cricket's leading scorer in 2004 with 1,426 runs, including five centuries.

The 34-year-old left-hander was man of the match after scoring 191 and 97 in last week's first Test win over Pakistan in Perth.

New South Wales captain Simon Katich has been put on standby.

"It is expected that if Justin can't play, then Simon will open the batting with Matthew Hayden, " Australia chairman of selectors Trevor Hohns said in a statement.

"He is a versatile batsman and a quality player who can bat in a variety of positions."

Katich, who normally bats in the middle order, will train with the Australia team in Melbourne on Friday.

He missed Australia's two home Test wins over New Zealand last month and the first Test against Pakistan after failing in the fourth Test against India in Bombay last month.