An instrument interface of a robotic manipulator and a surgical system including the instrument interface are provided. In one embodiment, the instrument interface includes a spring-loaded input for providing axial load and torque to a sterile adaptor capable of operably coupling an instrument. In another embodiment, a robotic surgical manipulator system includes a manipulator assembly, including a base link operably coupled to a distal end of a manipulator arm, and a carriage link movably coupled to the base link along a lengthwise axis, the carriage link including an integrated instrument interface. The system further includes an instrument operably coupled to the carriage link via the instrument interface, and a processor operably coupled to the manipulator assembly for sensing presence of the instrument.