And then it covers all of them. The whole market. It's like if you owned a ranch house on a beach and that caused you to become the owner of every ranch house on every beach, and if someone built a new one somewhere else on some land that isn't yours then you would become the owner of it too. That's not how real property works.
And you're confusing the value of the market with control over it. It's possible to have a total monopoly on some useless junk nobody wants.
In theory that's the test, but it doesn't actually work. In practice market power isn't binary. There is always a substitute for anything if you jack the price up high enough. And a monopolist would jack the price right up to that point, so that increasing it any more would cost sales.
But the zero volume case is the divide by zero case anyway. A test isn't going to give you a yes or no, it's going to give you NaN. That doesn't mean there is no market power, it only means you can't tell without a buyer. And in the patent case, as soon as there is a buyer there is market power.