In 16 seasons as a professional, Madison Keys had carved out a successful career in tennis. She won nearly 300 matches, almost $20 million in prize money and settled into a comfortable spot as a Top 20 player.
The only thing missing over the years was a Grand Slam title, something her exceptional gifts once suggested was not only possible — but probable. That began, Keys said, when she was 11.
Early last year, as her relationship with Bjorn Fratangelo deepened, they began to seriously discuss her future. Fratangelo — destined to become her husband and coach — wondered this aloud:
When is good enough not good enough?
“It was just kind of like how much do you want to get out of this?” Fratangelo told…