Preheat oven to 375°F. Lightly grease a 13” x 9” baking dish.
On a baking sheet, bake sweet potatoes for 1 hour or until done. Let cool, then peel and mash. Reduce oven to 350°F.
In a bowl, combine mashed sweet potatoes, Splenda Sweetener, flour, milk, orange juice, egg, vanilla extract, orange zest, and 3 tablespoons melted butter. Using an electric mixer, beat on medium speed until smooth. Transfer to baking dish.
In a bowl, combine breadcrumbs, pecans, syrup, and remaining 2 tablespoons melted butter. Sprinkle over top of casserole.