A surgical apparatus comprising: a surgical instrument manipulator assembly (240, 440, 940, 1040, 2040) comprising a drive output assembly and a preload assembly (480,1080), the drive output assembly comprising a drive output disk and a preload spring assembly operatively coupled to the drive output disk; and a sterile adapter assembly (250, 450, 2050) removably mountable to the drive output assembly of the surgical instrument manipulator assembly, the sterile adapter assembly comprising an intermediate disk and a release button (961, 962), and the intermediate disk being configured to releasably engage with the drive output disk of the drive output assembly in a mounted state of the sterile adapter assembly to the drive output assembly, wherein: in the mounted state of the sterile adapter assembly to the drive output assembly, the sterile adapter assembly is latched to the surgical instrument manipulator assembly and is removeable from the surgical instrument manipulator assembly in response to actuation of the release button; the preload assembly (1080, 2080) comprises a disengaged state in which the preload assembly configures the preload spring assembly to not apply a preload force on the intermediate disk and an engaged state in which the preload assembly configures the preload spring assembly to apply a preload force on the intermediate disk; and in the engaged state of the preload assembly, the surgical instrument manipulator assembly does not inhibit actuation of the release button, and the sterile adapter assembly is removable from the surgical instrument manipulator assembly in response to actuation of the release button. a surgical instrument manipulator assembly (240, 440, 940, 1040, 2040) comprising a drive output assembly and a preload assembly (480,1080), the drive output assembly comprising a drive output disk and a preload spring assembly operatively coupled to the drive output disk; and a sterile adapter assembly (250, 450, 2050) removably mountable to the drive output assembly of the surgical instrument manipulator assembly, the sterile adapter assembly comprising an intermediate disk and a release button (961, 962), and the intermediate disk being configured to releasably engage with the drive output disk of the drive output assembly in a mounted state of the sterile adapter assembly to the drive output assembly, a drive output assembly and a preload assembly (480,1080), the drive output assembly comprising a drive output disk and a preload spring assembly operatively coupled to the drive output disk; and a sterile adapter assembly (250, 450, 2050) removably mountable to the drive output assembly of the surgical instrument manipulator assembly, the sterile adapter assembly comprising an intermediate disk and a release button (961, 962), and the intermediate disk being configured to releasably engage with the drive output disk of the drive output assembly in a mounted state of the sterile adapter assembly to the drive output assembly, the sterile adapter assembly comprising an intermediate disk and a release button (961, 962), and the intermediate disk being configured to releasably engage with the drive output disk of the drive output assembly in a mounted state of the sterile adapter assembly to the drive output assembly, wherein: in the mounted state of the sterile adapter assembly to the drive output assembly, the sterile adapter assembly is latched to the surgical instrument manipulator assembly and is removeable from the surgical instrument manipulator assembly in response to actuation of the release button; the preload assembly (1080, 2080) comprises a disengaged state in which the preload assembly configures the preload spring assembly to not apply a preload force on the intermediate disk and an engaged state in which the preload assembly configures the preload spring assembly to apply a preload force on the intermediate disk; and in the engaged state of the preload assembly, the surgical instrument manipulator assembly does not inhibit actuation of the release button, and the sterile adapter assembly is removable from the surgical instrument manipulator assembly in response to actuation of the release button. in the mounted state of the sterile adapter assembly to the drive output assembly, the sterile adapter assembly is latched to the surgical instrument manipulator assembly and is removeable from the surgical instrument manipulator assembly in response to actuation of the release button; the preload assembly (1080, 2080) comprises a disengaged state in which the preload assembly configures the preload spring assembly to not apply a preload force on the intermediate disk and an engaged state in which the preload assembly configures the preload spring assembly to apply a preload force on the intermediate disk; and in the engaged state of the preload assembly, the surgical instrument manipulator assembly does not inhibit actuation of the release button, and the sterile adapter assembly is removable from the surgical instrument manipulator assembly in response to actuation of the release button.