Samantha Stosur's stranglehold as Australian top women's tennis player is in jeopardy thanks to the superb form of compatriot Daria Gavrilova.
Following a run through to the final of the Kremlin Cup tournament in Moscow last week, Russian-raised Gavrilova has rocketed up the rankings from world No.37 to No.24.
She's now knocking on the door of top spot in Australia amongst the women, with 2011 US Open champion Stosur down to No.20 in the world on Monday.
While conceivably one good tournament away from taking over a mantle that Stosur has held since 2009, the veteran should have Gavrilova covered in the short term.
Stosur has the advantage of already being accepted into the WTA Elite Trophy event in China starting November 1.
The tournament, which plays second fiddle to this week's WTA Finals for the world's top eight players in Singapore, is nominally open to players ranked from No.9 to No.19.
But injury and withdrawals mean Stosur has already been accepted into the tournament while Gavrilova is touch and go to make the field as she's five spots below the initial cut-off.
Gavrilova will also need to hit the ground running in 2017 just to avoid going backwards in the rankings - she has to defend points from a fourth round appearance at the 2016 Australian Open.
Stosur was a first round loser at the event.
Still, it has been a golden few months for Gavrilova who has reached the last eight or better in her last three tournaments and is guaranteed a seeding at Melbourne Park in January.
At this point in time however sha may be simply looking for a rest.
She tweeted on Sunday: "Last three weeks QF in Beijing SF in Hong Kong F in Moscow in singles and doubles Not a single day off! Happy and exhausted!"
