A control valve assembly includes a valve body defining an inlet, an outlet and a fluid flow pathway therebetween. A ball valve is positioned within the fluid flow pathway and includes a rotatable ball having an inlet opening, an outlet opening and a flow pathway therebetween, an upstream seat ring positioned at an inlet side of the ball, and a downstream seat ring positioned at a downstream side of the ball, the seat rings being configured to substantially seal off fluid flow between upstream and downstream sides of the ball except through the ball fluid flow pathway. At least one of the upstream and downstream seat rings is a dynamic sealing seat ring. A retainer ring is positioned between the dynamic sealing seat ring and a portion of the rotatable ball to substantially prevent deformation of a portion of the dynamic sealing seat ring in a direction toward the ball.