You have to go back to February 2013 to find the last time a player other than Serena Williams topped the WTA rankings.
However, the 22-time grand slam champion could be deposed as world number one by three different players following the US Open.
Angelique Kerber, who would already have surpassed Serena had the German not been beaten by Karolina Pliskova in last week’s Western and Southern Open final, Garbine Muguruza and Agnieszka Radwanska all have a chance of taking top spot at the year’s final major.
We take a look at what each player requires to reach number one and their form heading to Flushing Meadows.
The current world number one is sure to match Steffi Graf’s record of 186 consecutive weeks atop the rankings, but can Williams make it to 187?
Serena is defending more points than any of her nearest rivals this week, having made the semi-finals of last year’s US Open before suffering a shock defeat to Roberta Vinci.
While a victory for the American would ensure she retains top spot, anything less leaves her vulnerable to Kerber. If the Australian Open champion reaches at least the last eight, Williams must win at Flushing Meadows to retain top spot.
With six US Open titles to her name, Williams has reason to be confident, although it remains to be seen if a relative lack of activity in an injury-interrupted season will count against her. The 34-year-old’s recent appearance at the Rio Olympics, where she was hampered by an apparent shoulder problem in a shock third-round defeat to Elina Svitolina, was only her seventh tournament outing of 2016.
Like Williams, Kerber – who has also made the Wimbledon and Olympic finals in 2016 after winning at Melbourne Park – knows a US Open victory will guarantee the number-one ranking.
With few points to defend, she could even reach top spot without winning a match, although that would only happen if Serena bows out before the last-four stage and both Muguruza and Radwanska fail to make the final.
The most consistent player on tour this year, Kerber ended 2015 as the world number 10 but has since reached six finals, winning two.
Muguruza’s equation is more straightforward.
If the Spaniard wins the US Open, she will move to number one providing Kerber is not the runner-up.
A place in the final could also be enough for Muguruza to reach the rankings summit for the first time, but only with significant help from elsewhere, in particular an early exit for Kerber.
After claiming her maiden grand slam title at Roland Garros in June, Muguruza was an early casualty at the Mallorca Open and Wimbledon before bowing out in round three of the women’s singles at the Olympics.
Fourth seed Radwanska must win at Flushing Meadows to have any chance of moving to number one, unless she takes the title at New Haven this week – in which case a runner-up spot could prove enough providing her rivals all falter.
A quarter-finalist in Cincinnati last week, the Pole started the year in good form but has not made a final since winning January’s Shenzhen Open.