Using hydrodynamic simulations we study the shear-induced unfolding of a collapsed polymer near a planar wall. Above a well-defined threshold shear rate , the globule becomes unstable and displays stretching-refolding events. With decreasing distance from the surface, the critical shear rate goes down, which is rationalized within a scaling analysis in terms of increased hydrodynamic stress due to a surface-induced slowing-down of globule rotation and translation. Our results are relevant for protein-assisted blood clotting in capillary vessels.