In the 1980s the game of tennis became extremely fast. Racquet technology, new training regimens, and fast, hard courts placed a premium on first strike tennis and hitting everything as hard as possible. But the game has changed. Courts are slower (even the grass!) and string technology is giving players access to greater topspin and control than ever before.
First strike tennis no longer works. To be a champion in tennis today players must be able to create and adapt, to attack and defend, to lose an agonizingly long point and still be ready for the next one. These attributes are best learned on clay.