Preheat your oven to 375°F (190°C) and lightly grease a 9x13 inch baking dish.
Bring a large pot of salted water to a boil. Carefully place the whole head of cabbage in the water. Boil for 3-5 minutes, peeling off the outer leaves with tongs as they soften. You will need about 12 large leaves. Pat them dry and cut out the thickest part of the vein at the bottom of each leaf.
In a large mixing bowl, combine the ground beef, cooked rice, chopped onion, minced garlic, Worcestershire sauce, salt, and pepper. Mix until well combined (using hands is best).
In a separate medium bowl, stir together the tomato sauce, diced tomatoes, dried oregano, and dried thyme.
Spread a thin layer (about 1/2 cup) of the tomato mixture onto the bottom of the baking dish.
Place about 1/3 to 1/2 cup of the meat mixture onto the center of a cabbage leaf. Fold in the sides and roll up tightly, burrito-style. Repeat with remaining leaves and filling.
Arrange the cabbage rolls seam-side down in the prepared baking dish.
Pour the remaining tomato sauce mixture evenly over the rolls.
Cover the dish tightly with aluminum foil and bake for 60 minutes, or until the cabbage is tender and the meat is cooked through.
Remove the foil, sprinkle the shredded mozzarella cheese over the top, and bake uncovered for another 10-15 minutes until the cheese is melted and bubbly.