Elena Rybakina (left), and Aryna Sabalenka

Elena Rybakina ended Zheng Qinwen's US Open campaign with a 3-6, 6-1, 6-4 win in the quarterfinals on Wednesday and became the new world No. 1 for the first time in her career.Rybakina confirmed she will replace Aryna Sabalenka at the top of the world rankings on Monday with her victory over China's Zheng Qinwen.The 27-year-old from Kazakhstan came back after losing the first set to book a place in the semifinals, where she will face former US Open champion Coco Gauff for a spot in the final.By reaching the semifinals, Rybakina was guaranteed to replace Aryna Sabalenka at the top of the WTA rankings, even if Sabalenka goes on to win the US Open title.Rybakina is the first player from Kazakhstan, male or female, to become world No. 1 in singles. She is also the 30th player in WTA history to reach the top ranking.Sabalenka's run as world No. 1 ends after 99 consecutive weeks. She has spent 107 weeks in total at the top and her 99-week streak is the sixth-longest consecutive reign in WTA history. She had held the No. 1 ranking since October 21, 2024.Rybakina has been one of the closest challengers to Sabalenka throughout the season. She arrived in New York along with Jessica Pegula and Coco Gauff as the three players who could take over the top ranking. Pegula and Gauff both needed to win the US Open title and hope Rybakina was eliminated before the semifinals.Gauff also reached the semifinals after saving two match points in a 2-6, 7-6 (9/7), 6-2 win over 19-year-old Mirra Andreeva, the French Open champion from Russia."Elena is the new world number one," Gauff said. "It's going to be a tough match. These are the moments you live for."Rybakina is chasing her third Grand Slam title after winning Wimbledon in 2022 and the Australian Open earlier this year.The world No. 1 ranking is a milestone, but Rybakina said her focus remains on winning tournaments."It's just a number right now. My goal is to win the tournaments which I play," the 27-year-old said."It's an amazing achievement, but you know how quickly everything can change in tennis ranking-wise."If both players win their semifinal matches, Rybakina and Sabalenka could meet in the US Open final, just as they did at this year's Australian Open, where Rybakina won in three sets. Sabalenka will face Jessica Pegula in the other semifinal.