Clay is a great surface for developing some of the key aspects of the game for success at the next level, including the ability to play defense, counterpunch and be steady, as well as work a point effectively and move efficiently on the court. Clay forces you to develop those skills or you won't win, where hard courts definitely don't accentuate those aspects of the game as much. The Europeans have done it well, and you hear the phrase often "aggressive shots to conservative targets" - those guys can work a point effectively and get opponents off balance, while still playing percentage tennis. Novak's ability to create incredible points while keeping match unforced error numbers low has been amazing to watch the last few years. There are a bunch of them though that are spectacular players.

It's almost one of those sports where you have to make some noise in the ATP tour by age 17-20 as well. If you are playing college, you likely won't play pro, for the most part, because if you were going to play pro, you'd be on the tour at that age instead of playing college. There obviously have been multiple exceptions to that rule, such as Isner and Stevie Johnson who have done relatively well. Overall though, the best shot is to do well in the international junior tourneys and get to to the level where you can make it on the tour in your teens. I have a buddy who tried to crack into the tour through futures and satellites after college, and it was brutal. He played for a few years, but eventually the expense of traveling and difficulty of the tourneys made it not worth it. Excellent college player too, but that international pro level was something else. It's a tough sport to successfully break into.

You're right that Sloane has dropped off, she looked very promising there for a while. The women definitely do have better prospects and possibilities for top players compared to the US men right now. After her Roland Garros performance, it will be interesting to watch Anisimova's performance and trajectory over the next few years. I also agree with you that Serena might be at the end of her line, Wimbledon will be telling.