Simona Halep. (AP Photo)

Simona Halep is currently the world No. 1, but how long will it last? She has had some high and low points throughout this season, and suffered a herniated disk which forced her to withdraw from Beijing.

While some questioned whether she would end her season early, she insists she will definitely be heading to Singapore for the WTA Finals. She's defending 500 points at the WTA Finals, and is still entered in Moscow. 

Her year-end No. 1 ranking is almost clinched. One possible, though unlikely scenario, is 20-year-old Naomi Osaka storming to the top spot. She's into the Beijing semifinals, has only 60 points left to defend in 2019, is entered in Hong Kong and will be making her Singapore debut (where the maximum points is 1,500). 

Caroline Wozniacki is also into the Beijing semifinals, but has a whopping 1,375 points to defend in Singapore after winning it last year. Angelique Kerber rounds out the Top 4, and she has just 80 points left to defend this season.

While Halep may still be the year-end No. 1, someone is going to take the throne from her eventually.