We discuss how to generalize the Riemannian concept of "rank" to the CAT(0) setting, in the case that the CAT(0) space satisfies the duality condition. (The duality condition is equivalent to the following property: the set of \Gamma-recurrent geodesics is dense, for some subgroup \Gamma of the isometry group. In the Riemannian setting this condition is implied by cocompactness.)