We investigated the dynamics of gold nanoparticles (NPs) within an entangled liquid of poly(n-butyl methacrylate) (PBMA) above the glass transition temperature (T-g). The experiments were performed by using a modified version of fluctuation correlation spectroscopy (FCS), which measured the translational diffusion (D) of the isolated NPs as a function of their size (2R(0) = 520 nm) and temperature (T). We probed the most interesting but sparsely investigated length regime where the particle size/tube diameter (d) ratio ranges between similar to 14. This allowed us to put into direct test recently developed theories and simulations. By measuring the bulk viscosity of the melt, the ratio D/D-SE was determined, where DSE is the continuum prediction from StokesEinstein (SE) relation. Our results indicate gradual recovery to SE behavior and full coupling to entanglement relaxation would require 2R0 approximate to 710dt.