Jack Sock has had the sort of tennis career that most players can only dream of — an Olympic gold and bronze medal in 2016, as well as career-high worldwide rankings of No. 8 in singles and No. 2 in ...

The question has circled the sport of professional tennis for the past several years, ever since a one-time wunderkind ranked in the worldwide top 10 started plummeting. Whatever happened to Jack Sock ...