The attacker suffered a thigh injury a day before their home game against Burnley.
The medical staff are not 100 percent certain when he will be back.
But Hasenhuttl is a bit pessimistic about the injury.
He told reporters: "There is still a little bit of blood so that will take time.
"I think about one month, hopefully not longer.
"It's maybe after the international break that he can play again.
"That's the schedule at the moment and hopefully it works."
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