We're only into the first week of the 2018 season, but a fierce battle for the top spot in the WTA rankings is already underway.

Less than 200 WTA ranking points separate world No. 1 Simona Halep (6,175) from Garbiñe Muguruza (6,135) and Caroline Wozniacki (6,035). Muguruza was forced to retire with cramps in her opening-round match against Aleksandra Krunic at the Brisbane International in Brisbane, Australia, but Halep is safely through to the second round at the Shenzhen Open in Shenzhen, China, and Wozniacki has reached the last 16 at the ASB Classic in Auckland, New Zealand.

Should Halep win her second-round match against Ying-Ying Duan of China, she will keep her current standing for at least another few weeks. However, if she loses against Duan and if Wozniacki wins the title in Auckland, the Dane will take the top spot for the first time since January 2012, marking the longest gap between stints at No. 1 in WTA history.

All three players are scheduled to take next week off, which means the Australian Open could also bring about a new No. 1. Both Halep and Wozniacki suffered surprise first-round defeats last year, while Muguruza amassed 430 WTA ranking points by reaching the quarterfinals.

Halep and Muguruza have yet to reach the semifinals in Melbourne, while Wozniacki did once in 2011. The Romanian and the Dane are eager to win their first Grand Slam titles this month, while Muguruza looks to move closer to completing a career Slam after prevailing at Roland Garros (2016) and Wimbledon (2017).