1. Cut chicken diagonally into 1/2-inch-thick slices; set aside. In a 3-1/2- or 4-quart slow cooker, stir together pasta sauce and Worcestershire sauce. Add onion and chicken slices.
2. Cover and cook on low-heat setting for 4 to 5 hours or on high-heat setting for 2 to 2-1/2 hours.
3. To serve, spoon chicken and sauce mixture over bun halves. If desired, sprinkle with crumbled bacon and tomato. Serve with dill pickles, if desired. Makes 6 servings.