Systems and methods are provided for processing blood or a fluid containing blood plasma and platelets. The blood or fluid is continuously added into a fluid separation chamber, which is used to isolate platelet-rich plasma therein. At least a portion of the platelet-rich plasma is automatically transferred from the fluid separation chamber into an injection device, with the fluid separation chamber and the injection device comprising components of a disposable flow circuit, which may be a closed system. One or more injection devices may be connected to a collection container or a pump device of the disposable flow circuit.
