Jay, with all due respect I do not agree with what you say here.
The term "natural talent" is thrown around very often when people mention someone very skilled in any sport be it tennis, golf or pool. The use of this term overshadows a lot of other things that were of more importance like dedication, drive to win, practice hours, mindset, heart and various others.
There are always going to be people who have more physical or mental advantage over others but if they don't practice and do the hard work that "natural talent" is going to get them nothing. Let's say if I want to be a basketball player but cuz of my height (5'6) it is going to take a lot to make it to NBA. So, it's apparent here that I don't have any natural talent (height) for this game and so if I want to break in to pro scene I will have to try harder than other guys or do some ground breaking changes.
All the professionals be it in any sport work 'harder' in one way or other than the armatures. Ask any top professional in any sport the question "hey was it easy for you to be here at the top of sport since you got a lot of natural talent ?". What you think they will say?
You wrote .
The difference in "ability" could be something else that we can't put our finger on. So a lot of times it's just easier to say it "natural talent". Now, that's not saying I can get any random person from street and they can be a top pro. No, that's probably not going to happen but at least they can be taught to play at high level. There are always people who have certain advantage over others and that is just a fact of life be it physical or mental.
What bothers me that people give "natural talent" more credit than what it deserves.
Here is a good article about natural talent :-
http://www.blueprinttennis.com/featured/natural-talent-fact-or-fiction/