A article of footwear having an upper and a sole structure secured to the upper. At least a portion of the upper includes a substrate layer and a polymer layer. The substrate layer is formed of an air-permeable material, and may be a textile or mesh material. The polymer layer defines a plurality of apertures that expose portions of the substrate layer, and the polymer layer is formed of a polymer material that infiltrates the substrate layer and is thereby secured to the substrate layer. A method of forming the material for the upper includes casting a polymer resin to form the polymer layer.