Hard to say for certain from that picture - especially since its blurry and I can't see the leaf edges or really much else that would help.
But, a guess would be a juvenile Chokecherry. Most have some extremely fine teeth on the leaf edge, but I have seen some almost smooth as well. In fact, there is one in the fence row of my yard that has smooth edges. To complicate matters, the multiple species can hybridize and create an essentially new Chokecherry.