I am sure you remember the monica seles story.
When a deeply disturbed German man named Gunter Parche approached the court during a changeover, grabbed a nine-inch boning knife with two hands and stabbed Seles in the back -- April 30, 1993 -- his mission was horrifyingly complete: Steffi Graf, the object of his obsession, eventually regained the No. 1 ranking from Seles, then just 19 and sensationally on the rise.
The wretched man didn't realize that Graf's career would, in fact, be tainted -- or that Graf would be appalled at the notion of Seles vanishing from tennis in such a manner. He ruined everything for everybody, with the possible exception of himself. Over the course of two trials, Parche was deemed to be so deranged as to be incapable of reason and no longer a threat to anyone. He never served a moment of jail time.
so we have plenty of these disturbed people roaming the globe. nadal is one of the highest profile global sports superstars. he should not take any chances.