He's going very slowly and they are testing his reaction to heavier exercising, seeing how the knee will react.
It's just unknown yet, wouldn't count on him.
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Actually they probably don't count on him, that's why Lemina was brought.
Khedira may actually be healthy for a while.. but he wouldn't make much difference, except providing rest for Pogba/Pereyra/Hernanes/Marchisio.