Birmingham to bag Villa midfielder Gardner
The former England under-21 international will move to St Andrews subject to passing a medical and agreeing personal terms.
The 23-year-old, who can also play at fullback, has made 79 appearances for Villa, who he joined as a trainee.
"Craig is a versatile and dynamic player who can perform in a number of positions," said City manager Alex McLeish.
"Players like that are really worth their weight in gold."
Birmingham said Gardner had supported City since childhood.