A draw? Apart from what you find in a dresser/wardrobe there is no such thing. How can 1 man draw ratings? Will he draw people who currently aren't wrestling fans? Is he gonna make people love wrestling? No!
The reason wrestling ratings are so poor is because wrestling isn't cool. Most people grow out of wrestling and it's not interesting enough to attract every single kid like it used to. Between that and the Internet, it's all but killed wrestling from the ratings aspect. That's why the ratings are down. Not because 1 man is champion or getting a push.
The only way you can see if someone is a draw and see how the ratings are.
Without Cena I feel people would slowly tune out.