Mechanical face seals are constitutive components of a much larger turbomachine. The interplay between the seal and the turbomachine is complicated by the trend of increasing turbomachine efficiency by reducing seal clearances, increasing rotor shaft speeds, and making rotors lighter and more flexible. These methods for increasing efficiency heighten the importance of incorporating the coupled rotordynamics into the seal dynamics. The principal objective of this work is to, for the first time, determine how the rotor affects the seal performance. Thresholds can then be established beyond which the rotor influences the seal performance but not vice-versa. A general model of a flexibly-mounted stator (FMS) face seal is provided including the coupled dynamics of the flexible shaft and seal seat. The model accounts for rotor and FMS axial and angular deflections. Specifically, a lumped-parameter model is used to simulate the rotordynamics (if required, a more complicated model is certainly permissible). Static and dynamic rotor angular misalignments are considered. For expediency, the EOMs are linearized in the non-contacting regime and solved analytically at steady-state to investigate rotor inertia ratio, shaft speed, and angular misalignment. Importantly, results reveal that in some operating regimes, neglecting the rotordynamics implies healthy seal operation when instead contact exists between the seal faces. The effect of rotor-stator inertia ratio is investigated, demonstrating that when the rotor inertia is much larger than the seal’s, the rotordynamics can be solved separately and sent to the seal model as an external input.