NEW YORK, NY, USA - What started as a field of eight women who could finish the US Open at No.1 has been whittled down to three. Heading into Labor Day weekend at the US Open, World No.1 Karolina Pliskova will look to hold off No.3 Garbiñe Muguruza and No.4 Elina Svitolina in the ongoing battle for No.1.

How we got here:

Pliskova, Muguruza, Svitolina, Simona Halep, Caroline Wozniacki, Johanna Konta, Svetlana Kuznetsova, and Venus Williams came into the US Open with a chance to finish the tournament with the No.1 ranking. Konta, Wozniacki, and Kuznetsova's early losses eliminated them from the chase, while Halep and Venus's chances ended on Friday after Muguruza progressed to the Round of 16 with a 6-1, 6-1 win over Magdalena Rybarikova.

By advancing to her first Round of 16 at the US Open, Muguruza is now in pole position for the top spot. After taking into account the points dropping off on the Monday after the US Open, when the new rankings will be released, Muguruza goes into the second week with 6,030 points. The challenge for Svitolina and Pliskova is to chase down the Spaniard. Svitolina currently has 5,640 points, and Pliskova, who is defending runner-up points in New York, is at 5,330 points. Both Svitolina and Pliskova are still in the third round. 

No.1 Scenarios:

Garbiñe Muguruza

Titles: Cincinnati (900), Wimbledon (2000)
Next Best: Rome (SF, 350), Australian Open (QF, 430), WTA Finals Qualifier (1-2 in RR, 500)

The 23-year-old is currently the frontrunner, as Svitolina and Pliskova will have to outperform her over the homestretch to have a chance at No.1. Muguruza is in the top half of the draw and Svitolina and Pliskova are in the bottom half. 

Muguruza can clinch the No.1 ranking outright if she wins the title. If she plays Pliskova in the final and loses, Muguruza and Pliskova would be tied with 7,090 points and the tiebreaker would be employed. In the event that two players are tied for the same ranking points, the first tie-breaker is ranking points earned at Grand Slams, Premier Mandatory events, Premier 5 events and the WTA Finals. If Muguruza and Pliskova end up in a tie, the tiebreak would go to Muguruza.

If Muguruza plays Svitolina in the final, the winner will be No.1. 

Muguruza is bidding to become just the second player in the last 14 years to win Wimbledon and the US Open in the same season and the youngest player to win two majors in a single season since Justine Henin in 2003. 

Elina Svitolina

Titles: Toronto (900), Rome (900), Istanbul (280), Dubai (900), Taipei City (280)
Finalist: WTA Elite Trophy Zhuhai (440)
Next Best: French Open (QF, 430), Beijing (SF, 390)

The 22-year-old Ukrainian needs to reach the semifinals in order to have a chance of moving to No.1. If Muguruza reaches the quarterfinal then Svitolina would need to reach the final in order to have a shot at No.1. Svitolina could clinch the No.1 outright if she wins the title. 

Svitolina leads the tour with five singles titles in 2017 and became the first player to win three Premier 5 level events in the same season by lifting the trophies in Dubai, Rome, and Toronto. The only other players to win two Premier 5s in a season -- Caroline Wozniacki (2010), Maria Sharapova (2011), Serena Williams (2013, 2014), Victoria Azarenka (2013) -- all reached World No.1.

Karolina Pliskova

Titles: Eastbourne (470), Doha (470), Brisbane (470)
Next Best: Cincinnati (SF, 350), French Open (SF, 780), Miami (SF, 390), Indian Wells (SF, 390), Australian Open (QF, 430), WTA Finals Qualifier (1-2 in RR, 500)

The current No.1 needs to reach the final in order to extend her stay at the top of the WTA Rankings, however, if Muguruza advances to the semifinals, then Pliskova would need to win the title. If Muguruza makes the final, Pliskova would no longer have a chance at moving to No.1. 

Pliskova has held the top spot for seven weeks, after becoming the first woman representing the Czech Republic and 23rd woman overall to hold the No.1 ranking after Wimbledon. The tour's "Ace Queen", the 25-year-old leads the tour in aces this season and has led the WTA in aces for the last two seasons.