Bjorn Borg
Credit: AP

Why he hung it up: The mysterious Swede did things his own way, but this quote from Arthur Ashe provides a hint into why he retired at 26: "He was bigger than the game. He was like Elvis or Liz Taylor or somebody."

Why he returned: Reflecting later on why he came back, Borg told a reporter: "I knew I was not playing well. But I can't explain it except to say I wanted to play."

His Success: In the early 1990s, he grew his hair long like it was before he retired and used a wooden racquet. His tennis suffered for it and he never won a tournament after coming back.