1. Preheat grill to medium-low. Combine mayonnaise, parsley, sage and garlic in a small bowl. Set aside.
2. In a large bowl, combine turkey, yogurt, Worcestershire sauce, mustard and salt. Mix gently with your hands. Form into 8 small 1/2-inch-thick patties.
3. Grill burgers, turning once, until an instant-read thermometer inserted into center of a burger reads 160ºF, about 15 minutes total.
4. Put burgers on bun bottoms and spread with mayonnaise mixture. Top and serve.