Whisk egg, mustard, Worcestershire sauce, salt, paprika, and pepper in a bowl, adding all vegetables and breadcrumbs. Combine and then add beef, kneading the mixture into a greased loaf shape pan. Spread ketchup on top.
Bake until the center reaches 165 degrees F (approximately 40 minutes). Rest for 8-9 minutes, pop out of pan, and slice.