A sleeve assembly for a combustion system is provided. The sleeve assembly includes a liner defining a combustion chamber having a flow axis and a primary combustion zone. The liner has a forward end and an aft end such that the liner circumscribes the flow axis. The sleeve assembly also includes a shell circumscribing the liner such that a cooling duct is defined between the liner and the shell. The shell includes a unisleeve having a forward end and an aft end. The aft end of the unisleeve is positioned axially upstream of the aft end of the liner, defining a gap between the aft end of the liner and the aft end of the unisleeve. The unisleeve is mounted to the liner at circumferentially spaced locations along an axial plane between the forward end and the aft end of the unisleeve.