How long will Muguruza keep her No. 1 ranking?

In early July, it looked like Garbine Muguruza was going nowhere. She had completed a mediocre clay-court swing and had not made a final in the 13 months since winning the French Open. She was ranked No. 15 and hardly a thought to challenge for the No. 1 ranking.

Two months later, she rose up the charts in record speed to the top and was the first to clinch a place for November’s WTA finals.

The 23-year-old Muguruza won Wimbledon and Cincinnati and increased her ranking 3515 points by the time she bowed out in the fourth round of the US Open. She replaced Karolina Pliskova who lost her top spot when she went down in the quarterfinals to American Coco Vandeweghe.

Muguruza joins ATP No. 1 Rafael Nadal for a Spanish monopoly atop tennis. It’s the first time Spain has jointly claimed both leaders. Muguruza is the second Spanish woman to be No. 1, 22 years after Arantxa Sanchez Vicario squeezed in 12 total weeks during the mid-90s reign of Steffi Graf.

With Serena Williams inactive for the time being and Angelique Kerber struggling, the top ranking has been up for grabs. Will Muguruza become a dominant No. 1, or will she flash around a rankings merry-go-round with Pliskova, Simona Halep, Elina Svitolina and others?

Muguruza’s 6,030 points are a slim advantage over Halep’s 5,640 points, while Svitolina and Pliskova are in range with 5,640 and 5,520 points respectively.

The Spaniard’s slump in late 2016 had her gaining only 281 rankings points following the US Open to the end of the year. She is in great position to add to her lead unless Halep outplays her in the Asian swing. Still, Halep has to defend 470 points, so Muguruza holds the advantage.

Svitolina must defend 820 points through November, so it will be hardest for her to get to No. 1 unless she has an epic run. Pliskova could make up ground to end 2017, but she has a lot more points to defend in early 2018.

All of this means that Muguruza has a great opportunity ahead. She will be in a battle with Halep over the next two months and might rotate the top spot, but she holds the highest chance of getting the year-end No. 1.