Nicole Gibbs is a twenty-three-year-old American tennis player, currently ranked No. 92 in the world. She might climb the rankings in the next few years—she was an indomitable national collegiate champion and stays in points with her sound defense; last March, at Indian Wells, I watched her play clean, aggressive, Top Twenty-level tennis, defeating, in straight sets, Madison Keys, who is now ranked No. 8 and is the best bet among U.S. women for the post-Serena Williams era. Or it’s possible that Gibbs might not get much further than she has: she’s five feet six and slender, and has neither a stroke nor a serve that she hits with commanding power—power being what the women’s game, like the men’s game, has by and large come to be about.

What Gibbs does not lack is a voice. In blog posts and on Facebook and Twitter, she has written more honestly and perceptively about what life is like for a pro tennis player than anyone since—well, since J. R. Moehringer co-wrote Andre Agassi’s autobiography. And over the past year or so, her writing has become more engagé: she’s opened her laptop at tournaments around the world to express her views on gun control, the refugee crisis, climate change, Black Lives Matter, Donald Trump, and, especially, all things that thwart or threaten equality for women. Gibbs can be emphatic, self-questioning, incisive, exploratory, a little peevish at times, and plenty funny. She’s never indifferent, or, apparently, disconnected.

Professional tennis has been for some time now the biggest platform available to women athletes, and other players do use it from time to time to carefully make a social or political statement. Serena Williams has spoken up about police shootings; Keys has addressed cyberbullying. Gibbs is different. She is outspoken in the way that Martina Navratilova was outspoken (and still is), or in the way that Billie Jean King was outspoken (and still is). She seems to wake up most every day with the desire to say something about what’s wrong with the world and how it might be made better.

Last week, I corresponded with Gibbs over e-mail, while she was in Australia preparing for the Australian Open, now getting under way in Melbourne. (In a tight first-round match, Gibbs upset twenty-eighth-ranked Timea Babos, a big and big-hitting Hungarian.) When I asked why she finds it essential to speak out as she does, she pointed me to the quote from Martin Luther King, Jr., on her Twitter page: “Our lives begin to end the day we become silent about things that matter.” She added, “I do feel that, as a female athlete, I have a unique responsibility to the feminist movement. Women have had a serious uphill battle for respect and reasonable compensation in the sports world. I think it’s important that female athletes (and especially tennis players) give a nod to pioneers like Billie Jean King by embracing feminism and continuing the push for equality.”

Gibbs grew up in Shaker Heights, the inner-ring Cleveland suburb, and has said that its efforts to become and remain a racially integrated town played a role in her outlook. Her father, a high-school English teacher who’d played tennis at Ball State, taught her to hit, beginning at age three—in the driveway, she told me, with a plank set atop two trash cans as a net. She was eleven when she won her first national title. She was a teen-age tennis prodigy in Los Angeles, where her family moved during her high-school years, and she earned a tennis scholarship to Stanford. She turned pro before finishing her degree in economics. She says now that she wishes she’d studied political science.

Her transition from Division I tennis to the pro tour has not been an easy one: for the first time in her playing career, wins became elusive and the losses piled up—and they had to be suffered alone, not with a team. It was her writing about this that first got my attention. At the end of 2015, she posted a brief account of her year. “Let me tell you a little bit about 2015,” it begins. “Of the 29 tournaments I competed in this year, I lost 15 first rounds.” She goes on to describe, with spare elegance, the many other losses, discouragements, and dark bouts of self-doubt that informed her year. It reads like a confessional list poem.

Following Gibbs, you see and sense what life is really like on tour in professional tennis when you aren’t at the top, surrounded by a team of coaches, fitness gurus, and nutritionist-chefs. You visit the near-empty side courts and the far-flung, second-tier, Challenger-circuit venues where most of her tennis gets played. There’s the goofy downtime stuff with fellow players, the hours of practice, the workouts, the stretching, the ice baths. And there are dives into the inner life of a young player, like the one Gibbs published on the Women’s Tennis Association’s Web site last spring, about a match she played against Garbiñe Muguruza, then No. 4 in the world, at the Miami Open. It was Gibbs’s first match on a center court, a night match attended by thousands:

“Ready, play.” The hum of the crowd turns to complete silence. When did it get so dark? I can’t make out a single face up in the stands. Wow, these lights are really, really bright. Everyone in the audience can see me, but I can’t see them, I can only hear that they’re there. It’s an eerie feeling. My head is spinning, and I’m feeling a little disconnected from my body. Somehow, I win the first game. And that would be the last game I won.

What haunted Gibbs about that loss in Miami was not the outcome itself—the stronger, more experienced big-match player had won, after all—but the possibility that her failure would be used by opponents she was battling off the court. One week earlier, Raymond Moore, the C.E.O. of the BNP Paribas Open, had told reporters that the women players “ride on the coattails of the men,” that those attending tournaments or watching at home were really interested in the great male players, and that the great male players were the ones driving the increases in prize money and television revenue. There are a number of players on the men’s side who agree with Moore—though Chris Kermode, the president of the Association of Tennis Professionals, which oversees the men’s tour, was quick to denounce Moore’s remarks. Serena Williams and other top women players, along with Billie Jean King, were outraged by what Moore said. But few were as vocal as Gibbs. She fumed, she tweeted, she urged reluctant players to speak out, she spoke out at a press conference organized by King and Chris Evert. (Evert later tweeted about Gibbs, “U r a future leader, girl . . .”) Moore apologized, and when that was not enough, he resigned.