Serena Williams overcame an early scare to defeat fellow American Sloane Stephens and move into the last 16 of the US Open on Saturday.
Williams, the third seed, lost the first set convincingly before rallying to dominate the next two, triumphing 2-6, 6-2, 6-2 inside a near empty Arthur Ashe Stadium.
Stephens, the 26th seed and 2017 US Open champion dumped Williams out of the 2013 Australian Open during her sensational run to the semi-finals as a 19-year-old.
And after dropping the opening set, Williams feared that she was about to fall victim to a major upset again.
“In that first set I don’t think she made any errors, honestly. She was just playing so clean and I just said, ‘I don’t want to lose in straight sets.’
The 38-year-old, gunning for a record-equalling 24th Grand Slam singles title, will play Greece’s 15th seed Maria Sakkari for a place in the quarter-finals.
Sakkari stunned Williams in three sets at the Western & Southern Open, a US Open tuneup, in New York last week. She beat another American, Amanda Anisimova, in the third round.
Unranked Bulgarian Tsvetana Pironkova extended her US Open giant-killing run on Saturday, scoring a second consecutive upset with a straight-sets defeat of 18th seed Donna Vekic.
Pironkova, who is playing her first tournament in three years, polished off Croatia’s Vekic 6-4, 6-1 in just over an hour.
The 32-year-old, who had eliminated 10th seed Garbine Muguruza in the second round, will face France’s Alize Cornet in the last 16, who progressed to the last 16 when Madison Keys retired injured.
Pironkova’s run to the fourth round equals her best performance at the US Open. She reached the last 16 in 2012, where she lost to Ana Ivanovic.
Pironkova only returned to tennis this season after taking a three-year break from the WTA Tour, during which she gave birth to her son in 2018
Second seed Sofia Kenin defeated Tunisia’s Ons Jabeur 7-6 (7/4), 6-3 to set up a match against Belgium’s Elise Mertens for a quarter-final place.
And former number one Victoria Azarenka said she had “a great opportunity” to end her seven-year wait for a third Grand Slam after booking a last 16 berth with a straight-sets win over Poland’s Iga Swiatek.
Alize Cornet (FRA) bt Madison Keys (USA x7) 7-6 (7/4), 3-2 retired
Tsvetana Pironkova (BUL) bt Donna Vekic (CRO x18) 6-4, 6-1
Maria Sakkari (GRE x15) bt Amanda Anisimova (USA x22) 6-3, 6-1
Serena Williams (USA x3) bt Sloane Stephens (USA x26) 2-6, 6-2, 6-2
Victoria Azarenka (BLR) bt Iga Swiatek (POL) 6-4, 6-2
Karolina Muchova (CZE x20) bt Sorana Cirstea (ROU) 6-3, 2-6, 7-6 (9/7)
Elise Mertens (BEL x16) bt Caty McNally (USA) 7-5, 6-1
Sofia Kenin (USA x2) bt Ons Jabeur (TUN x27) 7-6 (7/4), 6-3