A back injury will keep Justin Langer out of Friday's ING Cup cricket game against South Australia at the WACA as the West Australian captain targets a Pura Cup title.

Langer has a bulging disc on the left side of his back, an injury that nearly kept him out of the Boxing Day Test against Pakistan.

He re-injured his back training in Hobart on January 25 and missed the Warriors' Pura Cup victory over Tasmania last week.

Western Australia has moved atop the Pura Cup table on 30 points, ahead of the Blues (28) and Queensland (28).

Langer is desperate to steer WA to this season's title, with the state hosting crucial games against NSW and South Australia over the next four weeks.

Langer will also be part of the Test series against New Zealand starting in mid-March and has decided to miss the one-day match in Perth.

WACA physio David Edgar said Langer was responding well to treatment.

"Justin has received treatment twice a day since the re-occurrence and improved considerably," he said.

"He is still not 100 per cent fit and with the heavy schedule of play expected of him later this month it was considered an unreasonably high risk to play on Friday.

"Over time the bulge will repair with treatment and rest."

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