Already down with a hamstring injury he picked up in the last series against Zimbabwe, Clarke's position has been worsened by his troublesome back.
"Michael's got a recurrence of the hamstring injury that he had in Zimbabwe. It's not as bad as what it was in Zimbabwe but it's in the same location," Kountouris was quoted as saying by the 'Sydney Morning Herald'.
"He's also got a sore back. He's had an aggravation of his back - the two are tied together which makes it quite complex," Kountouris added.
Though he is yet to be officially ruled out of the first Test, Kountouris was not sure when asked how long would he take to regain match fitness.
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Clarke missed 10 weeks of cricket after breaking down in Zimbabwe at the end of August.
The 33-year-old will not play next week's Sheffield Shield match for New South Wales.
"We're still hopeful he might be right for the first Test because that's two weeks away but we need to review it again next week. He needs to start running and doing things before we make a decision on whether he's okay to start to play something.