The resilient modulus (MR) has been found to be the most important parameter in the Mechanistic-Empirical Pavement Design Guide (MEPDG) for the base layer. A literature review showed that the use of recycled asphalt pavement (RAP) in the base layer had many economic and structural benefits. The prediction of MR with the specific MEPDG model for the base layer mixed with RAP was found to be reliable for several field conditions. However, further studies of the MEPDG model are needed for an understanding of the physical meaning of each parameter in the model. The most important factor affecting MR for the base layer is the state of stresses, especially the confining pressure. This type of state of stresses was found in previous research to be more effective than deviator stresses. The present study focuses on the parametric analysis of each constant in the model versus various confining pressure states under various field conditions and at various RAP concentrations. This parametric analysis is compared with the traditional granular coarse aggregates used for the base layer before RAP is used so that any difference in the physical meaning when RAP is mixed in the base layer blend can be determined. The prediction of MR by the MEPDG model appears to be sound for RAP, but only with confining pressure levels below 10 psi and without significant variation in water content and maximum dry density. Freeze-thaw cycles do not negatively influence the prediction of MR for both RAP and granular coarse aggregates.