It is not so unusual for superstars to quit their sport, though they are normally drawn back in soon enough. Michael Jordan left the NBA at the peak of his powers and returned a year later after an unsuccessful attempt to reinvent himself as a baseball player. Johan Cruyff retired from football aged only 31 but quickly returned after losing a lot of money investing in pig farming.
What was unique about Bjorn Borg was that he conquered his sport, retired aged 26 and never returned, or at least not while still a competent tennis player. He reappeared 10 years later but lost every match he played.
