Pour the prepared cake batter into two round 9" cake pans that have been sprayed with nonstick spray. Bake the cakes as directed per the package directions. Once the cakes are baked, remove them from the oven to a cooling rack, covering each pan with foil; let the covered cakes cool completely.
Once the cakes are cooled, use a large knife to cut each cake in half, then slice a 1" strip from each half so that when the halves are placed together, side-by-side, they form a football. (You will have 2 footballs.) Frost each football cake with chocolate frosting, as desired.
Fill a pastry bag (fitted with a piping tip) with the buttercream frosting; pipe on the laces of each football cake. (If you don't have a pastry bag, use a freezer bag, cutting off the tip of one corner.)