Twenty-two years later, the details are fuzzy; but to Emma Hayes, the dilemma was clear. In the summer of 2002, at age 25, she was a rookie coach with an underperforming star — a star who doubled as her boss. In fact, Kim Wyant was the reason Hayes had her job. Wyant, coaching on an adjacent field in 2001, had overheard the charismatic Brit commanding a practice. She recruited Hayes to join the Long Island Lady Riders, a “female-first” amateur club; 90% of the gig, Wyant says, covered local camps and clinics, plus community engagement. The other 10% — three...