Quasi-3D nanoplasmonic structures are investigated, and the interaction of cavity and surface plasmon modes in Au cylindrical channels is discussed. By fastidious choice of geometrical parameters, it is shown that localized surface plasmon resonances (LSPR) inside the channels are established and are highly sensitive to changes in the local dielectric environment. In this study, cylindrical channels are added to the surface of gold nanopillars whose geometry otherwise permits LSPR. The inclusion of the channels creates a plasmonic waveguide supporting whispering gallery mode (WGM) cylindrical channel plasmons, which result from the coupled hybridized field. FDTD simulations reveal the possibility of single-molecule sensitivity of these cylindrical channel nanopillars (CCNP) by demonstrating near-IR wavelength shifts in the detected reflectance from a modeled array of CCNPs in various dielectric environments. The reported sensitivity of this metamaterial provides a platform for SPR single-molecule studies and exhibits potential for label-free biological and chemical sensing.