“I feel like I’ve done that,” Morgan Riddle tells me from her Melbourne hotel, reflecting on her five-year mission to make tennis cool again. “That” is her mission, which started five years ago, to get her chronically online female fan base into tennis. “The girls are at the tennis. So now I’m trying to figure out — what’s the next mission?”
It’s a good question for the 28-year-old who has become, according to The New York Times, “the most famous…

