I've been some people's rackets where the strings in the middle are worn down considerably more than the other parts, which suggests they're really good at timing the ball. But part of me also wonders if those good hits were done in a controlled environment against a ball machine or something. I've also seen videos of college D1 matches where the players more often than not, seem to hit outside the sweet spot, if not borderline shank the ball, but yet still produce great ball speed. so am i correctly assuming that the worn out stings at the sweet spots that I've seen come from repeated hits with a ball machine or coach, where the player knows exactly where the ball lands? Also, the ability to hit the sweet spot is dependent on your fundamentals and how well you can read the ball? Lastly, what are somethings you can focus on to hit the sweet spot more often? One thing I can think of is to focus on the point of contact.