  We derive an S=1 spin polaron model which describes the motion of a single
hole introduced into the S=1 spin antiferromagnetic ground state of Ca2RuO4. We
solve the model using the self-consistent Born approximation and show that its
hole spectral function qualitatively agrees with the experimentally observed
high-binding energy part of the Ca2RuO4 photoemission spectrum. We explain the
observed peculiarities of the photoemission spectrum by linking them to two
anisotropies present in the employed model---the spin anisotropy and the
hopping anisotropy. We verify that these anisotropies, and not the possible
differences between the ruthenate (S=1) and the cuprate (S=1/2) spin polaron
models, are responsible for the strong qualitative differences between the
photoemission spectrum of Ca2RuO4 and of the undoped cuprates.
