Smith damaged his ankle ligaments against Chelsea in early January and it was originally suggested that he would be back in action in a week or so but Smith's ankle has been slow to respond to treatment.
It has now been suggested that he may not be back until after the Milan game later this month.
"Nobody likes being injured, but sometimes you have to accept it," said Smith. "I didn't do myself any good trying to rush back to play against Chelsea. It probably set me back a few days. Now I am taking each day as it comes - and while I have not really set a date for my comeback, fingers crossed I will be fit soon."