Nonlinear shear data of an unentangled polystyrene melt [Santangelo, P. G.; et al. J. Rheol. 2001, 45(2), 583-594] are compared to Brownian dynamics predictions of Fraenkel chains. All parameters needed to perform the comparison are obtained from the known molar mass, zero-shear viscosity, and from older data for the linear glassy contribution [Inoue, T.; et al. Macromolecules 1991, 24(20), 5670-5675]. Comparison reveals that the magnitude of shear thinning of the unentangled melt cannot be explained unless account is taken of the flow-induced reduction of the monomeric (Kuhn segment) friction coefficient.