Johnson travelled with the rest of the squad on the recent tour of Austria, but the problem flared up again in training and the midfielder flew back to Birmingham for assessment.

Blues boss Alex McLeish revealed that summer signing Lee Carsley will deputise as skipper in Johnson's absence.

"Damien will have to have surgery on his back. He has resisted it over the last couple of years but now it is felt that an operation is best," McLeish told the club's official website.

"He will be out of action for no less than two months and we will support him 100% with the operation and rehabilitation.

"Damien is our club captain but because of his injury Lee Carsley will wear the armband when the new campaign gets underway. Lee has a vast knowledge of the game and is an excellent leader."