The study of shear-induced polymer crystallization has so far overlooked heterogeneous crystal nucleation of shish-kebab crystallites, which can be initiated by the stretched local polymer chains in the sporadic events of shear fracture upon sudden startup or cessation of polymer shear flow or in the memory of these events. We performed dynamic Monte Carlo simulations of a binary blend of short and long polymers and investigated the formation process of shish-kebab crystallites in a driven field with Poiseuille-flow-like gradient forces presumably generated around the shear layer of melt fracture. The results demonstrated the synergetic coil-extension and segregation behaviors of long-chain fractions upon precursor formation, which lead to a discontinuous crystalline structure along the shish. We found that the shear fracture hypothesis can reconcile several controversial experimental arguments on the precursor formation of shish-kebab crystallites in shear-induced polymer crystallization.