The German tennis star Angelique Kerber stands a good chance of becoming the No. 1 player in the world following the U.S. Open. PHOTOGRAPH BY EDUARDO MUNOZ ALVAREZ / AFP / GETTY

By the time Angelique Kerber played Victória Azárenka in Doha, in February, 2015, her career was in trouble. Kerber, who had finished 2014 ranked ninth in the world, had lost in the first round of the Australian Open, lost playing the annual team Fed Cup, lost in Dubai. After losing earlier that month, in Antwerp, to Francesca Schiavone, who was long past her Grand Slam-winning days, the German had dropped out of the top ten. It seemed only a matter of time before she was out of the top twenty.

In Doha, Kerber seemed barely in the game. She blocked back shots instead of swinging through them. She lunged, sent up desperate lobs, watched balls go by. She threw up her arms in frustration and frowned. She lost the first set 6–0, on an apathetic double fault. Before the start of the second set, she called her coach, Benjamin Ebrahimzadeh, even though both knew there wasn’t much to say. (The W.T.A. allows on-court coaching outside the majors.) "Stay in the rallies—work hard!" Ebrahimzadeh told Kerber. "But how am I supposed to play the rallies? I don’t win a point!” she said. He tried again. "I know it's difficult, but play your game!” “But my game doesn’t work!” she replied. Needless to say, she went on to lose the match.

I’ve been thinking about that moment a lot lately, because Kerber’s game now works extremely well. In fact, unless Serena Williams makes the semifinals of the U.S. Open next week or Agnieszka Radwańska wins it, the twenty-eight-year-old German will be the new No. 1 player in the world. This year, she has won the Australian Open, made the final of Wimbledon, taken home an Olympic silver medal, played deep into top tour-level events, and emerged as a legitimate threat to Williams. Kerber is one of the few players who can push the twenty-two-time major champion even when she is at her best.

Over the past year and a half, since that match in Doha, Kerber has become one of the most entertaining players to watch. She is a brawler whose game matches up well with big hitters, but also a smart, crafty, improvisational player with unusual strokes and a thrilling style. Her game is reactive but imaginative, using her opponent’s pace but also using her strength, especially in her legs, to redirect the power and make it her own. With her consistency, she baits her opponents into trying too much, while her shotmaking punishes them for their safe retorts.

Kerber turned pro in 2003, when she was fifteen, but she did not make much of an impact on tour until she reached the semifinals at the U.S. Open in 2011. Her rise was quick, but then she seemed to hit a wall. Part of the problem was that she played like a wall. She was known for her consistency—from tournament to tournament, shot to shot, point to point. But her consistency was almost a liability. She could get every ball back, but she rarely hit it past her opponents. She could make the quarters, the semis, even the finals, but she couldn’t knock anyone out. She had a weak serve, not much of a net game, and a tendency to retreat or become impatient. Sometimes she seemed to give up, or slap forehands out of frustration, or make sarcastic gestures. She had the tour’s best eye roll.

Why does her game work now? If you ask her, she can tell you a story. It has nothing to do with her technique or style, and everything to do with her mind. After those losses in early 2015, she decided that she needed to do something drastic. “I have to practice again,” she recalls telling herself. “I have to work really hard, and something has to change in my team.” She and Ebrahimzadeh parted ways, and she started working again with her old coach, Torben Beltz. Then, before playing in Indian Wells, in March, she spent a few days hitting with her compatriot Steffi Graf, who “got rid of my doubts,” though she is vague about what Graf said to her. Kerber says she then started hitting more aggressively (she uses the word “aggressive” a lot) and playing tough in tight matches. She won four titles in 2015, though she never made it to the late rounds of a major. She played Azárenka again in the third round of the U.S. Open, and again she lost. But this time it was different—perhaps the best match of the year. “It was not the feeling like I lost a match,” she told me. “It was more the feeling that I played good and she won it at the end, and this is what gives me a lot of confidence when I come to the new tournaments.”

She played Azárenka again in the quarter-finals of the Australian Open the following January. In previous years, that was the kind of occasion where Kerber might have felt the pressure and choked. But she beat Azárenka in straight sets, and then (after defeating Johanna Konta in the semifinals) went on to beat Williams, stunning the defending champion with perfectly timed returns, sharp cross-court passing shots, and delicate drop shots. Kerber had an explanation for how she kept her cool. In the W.T.A. finals last fall, during the round-robin portion, she had needed to win only one more set off of Lucie Šafářová in order to make the semifinals. But she had been too aware of it. “I told myself this will never happen again in my career,” she said this week. She told herself to forget the expectations placed upon her. “I will not think about this,” she instructed herself. “I will not speak about it.” Now that she has the chance to claim the No. 1 ranking, she is remembering that lesson. “I will not put too much pressuring on this,” she said at her first press conference at the Open. She talks about just “going for it” on her shots, being “aggressive,” and “not thinking” about what’s at stake. Tonight, she plays the young American CiCi Bellis in the third round.

What’s striking to me about that story is how much it leaves out. There is no room in it for the period of struggle right after winning her first major, when she crashed out of several tournaments early and lost in the first round of the French Open. (Her own explanation is that she needed time to practice, which she got this spring in Las Vegas, back with Graf.) Nor does it account for the fact that she sometimes still wavers at critical moments. Kerber has been in the finals of tournaments at Wimbledon, Cincinnati, and the Olympics—but she has not taken any of the titles. It doesn’t account for the way she played this week, in the second round of the Open, when she flew out to a 6–2, 4–1 lead against Mirjana Lučić-Baroni and then tightened, hitting loose errors that let Lučić-Baroni back into the set. (Kerber would win it 6–2, 7–6 (7).)

She is faster, but she was always fast. She has a remarkable ability to absorb and use her opponent’s pace, keeping close to the baseline and hitting her shots off her heels, but she hit that shot from a squat when she was a child. “I don’t practice it,” she said. “It comes to me naturally.” She has always had an unusual forehand. (A natural righty, she plays with her left.) She has good timing and an instinct for innovation, but she dismisses the suggestion that her style has changed, or that her decision-making process is different, or that her skill is much improved. When I asked whether she worked on improvising her shots, she said no, and gave a characteristic shrug. “I think this is my game,” she said.