I agree completely with the importance of diagnostic testing. However, part of that diagnostic testing must be to look at and understand the throwing motion of the player.
Let me give you an example of why I feel so strongly about this (and feel like I have something to contribute).
This year I had a young pitcher who, after throwing just 1 amazing inning in the first game of the year, started complaining of medial elbow pain. Being the hyper-cautious person that I am, I decided to not let him pitch again until I knew what was going on.
After playing catch with him, watching him throw a striped ball (so I could watch the spin of the ball), and understanding what seemed to bring on the problem (he thought he was throwing a fastball but seemed to be able to stall the ball out over the plate) his father and I realized that he was inadvertently throwing a slider. This was because he was supinating his wrist as he released the ball.
Now, this may admittedly be a somewhat different case since the pain came up out of nowhere and I could feel pretty confident that it could be correlated to the inning he pitched. However, I wouldn't have solved the problem by taking him to the doctor. They would have diagnosed him with an inflamed medial epicondyle, would have told him to not throw for 3 or 4 weeks, and would have left the underlying flaw in his motion untouched.
If you want to solve the problem, then you have to look at the big picture, not just the symptoms.