The degradation of the performance of distributed fiber Raman amplifiers (DFRAs) is shown to be dependent on the interaction between pump-pump four-wave mixing (FWM) and stimulated Raman scattering (SRS), by means of numerical simulations. We verify that FWM processes, including depletion and parametric gain, generate new sources of SRS and a redistribution of the pump power along the fiber. Results show impairments on the performance of DFRAs such as loss of flatness on the spectral gain and reduction on the Raman gain and presence of FWM products within the transmission band.