The 25-year-old midfielder joined the club on a free transfer from Steve Coppell's Reading last summer and has impressed during the last month when Chelsea have been hampered by the loss of four players on international duty in the African Nations Cup.
"Steve is important for us," said Grant.
"We didn't know we would have so many injuries but we knew that many players would go to the African Cup. This is one of the reasons we wanted him in the squad. In the last two games he has done a very good job.
"You have seen the quality of the squad in so many difficult times. I have a big satisfaction."