until losing to eventual champion Iga Świątek in the fourth round whilst only winning three games. As a result, she missed out on regaining the No. 1 ranking. Halep started 2021 at Gippsland, where she was defeated in the quarterfinals by Ekaterina Alexandrova. At the Australian Open, she also reached the quarterfinals, where she lost to Serena Williams. At Miami Open, she defeated Caroline Garcia, but she then withdrew due to a right shoulder injury. In April, at the Porsche Tennis Grand Prix, she defeated Markéta Vondroušová and Ekaterina Alexandrova, but lost to Aryna Sabalenka in the semifinals. At the Madrid Open, she beat Sara Sorribes Tormo in first round and Zheng Saisai in second round, but eventually lost to Elise Mertens in the third round. At the Italian Open, she retired during her match with Angelique Kerber after tearing a muscle in her left calf . Having not recovered from her calf injury in time, Halep withdrew from the French Open. Having still not recovered from her injury, Halep withdrew from Wimbledon, where she was the defending champion from 2019. As a result of not defending her 2019 Wimbledon points, her ranking fell to 13, dropping her out of the top 10 for the first time since January 2014 and ending a streak of 373 straight weeks in the Top 10, the 8th longest in WTA history. Halep returned to play at the Canadian Open and received a bye into the second round where she was upset by Danielle Collins in three sets. Halep won her first match back since her calf injury at the 2021 Western & Southern Open against Magda Linette in the first round. However, Halep withdrew from her second-round match with an injury to her right adductor. Halep finally returned to action in a Grand Slam event as she defeated Camila Giorgi in straight sets in the first round of the US Open. She then defeated Kristína Kučová and Elena Rybakina in the next two rounds to reach the round of 16 for the fourth time in her career. However, she failed to reach the quarterfinals of the US Open after a straight-set defeat by Elina Svitolina. She finished the 2021 season at No. 20; previously she had finished each year starting with 2014 in the top 5. 2021 was her first season since 2012 where Halep did not win a WTA singles title. 2022: