We develop an interpretation of the off-equilibrium dynamical solution of mean-field glassy models in terms of quasi-equilibrium concepts. We show that the relaxation of the `thermo-remanent magnetization' follows a generalized version of the Onsager regression postulate of induced fluctuations. We then find the rationale for the equality between the fluctuation-dissipation ratio and the rate of growth of the configurational entropy close to the asymptotic state, found empirically in mean-field solutions.