"He has still got severe discomfort in his knee and he was very, very sore yesterday after playing in the reserves," Blues boss Steve Bruce told the clubs official website.
"He doesn't seem to be improving having had one operation and it's not looking very good for him.
"We are going to give him another week to ten days to rest up and see if he can recover. If not then he will probably need another operation."
Graingers last appearance for Blues came in the FA cup defeat at Fulham in January when he rushed back from the initial knee injury and then had to begin his rehabilitation all over again.
