The 23-year-old Swiss international suffered a thigh strain in last weekend's home win over Bournemouth and according to manager Mark Hughes, may miss Saturday's trip to Villa Park.
"We will have to see how he is over the coming hours, because he hasn't trained with the group yet this week," Hughes said on Thursday.
"He will go home and rest now and hopefully he can come in tomorrow and join in the session with the rest of the lads. If he does that, and suffers no effects from it, then he will certainly be in my thoughts. If not then we won't take any chances."