Two of those players have had especially good seasons. Krejcikova, long a doubles star, has made good on her goal to bring her singles level up, as has her doubles partner, Katerina Siniakova. Usually, one member of a doubles team decides to focus on doubles and the team either breaks up or plays fewer events together, but these two--so far--are doing it all. For her part, Krejcikova upset fifth seed Elina Svitolina to advance to the final sixteen.
The other player who has had a "long time coming" boost this year is Cirstea, who recently won her first singles title in thirteen years, and then immediately went on to be a tournament runner-up.
Three former finalists, Stephens (2018) Marketa Vondrousova (2019) and Sofia Kenin (2020), are in the round of 16 draw, as are two former champions--Serena Williams (2002, 2013, 2015) and Iga Swiatek (2020).
One-quarter of the draw is occupied by players from the USA--Stephens, Kenin, Williams, and Coco Gauff (Gauff's third round match against countrywoman Jen Brady came to an end when Brady retired with a foot injury).
Last year, Paula Badosa reached the round of 16, in which she was defeated by clay court specialist Laura Siegemund. Badosa, who won a grueling three-hour contest against Ana Bogdan in the third round, is most likely engaged in heavy recovery work--both physical and mental--so that she can be reasonably fresh for her next match.
Here is the round of 16 draw:
Ons Jabeur (25) vs. Coco Gauff (24)
Sloane Stephens vs. Barbora Krejcikova
Sofia Kenin (4) vs. Maria Sakkari (17)
Marta Kostyuk vs. Iga Swiatek (8)
Serena Williams (7) vs. Elena Rybakina (21)
Vika Azarenka (15) vs. Anastasia Pavlyuchenkova (31)
Tamara Zidansek vs. Sorana Cirstea
Marketa Vondrousova (30) vs. Paula Badosa (33)