In the space of a month, Coco Gauff has levelled up and changed her narrative in the most forceful way possible.
The American teenager has been a tour mainstay since 2019, and for most of those four years the focus has been on her age and potential. Ever since reaching the second week of Wimbledon at 15 years old, Gauff has been setting notable youngest-since milestones; at 19 years old and ranked No.6, she remains streets ahead of her peer group.
But despite a maiden Grand Slam final at Roland Garros 2022, a counter-narrative began to build. Attention turned to her 0-7 record against World No.1 Iga Swiatek, in which she had lost all 14 sets they had played; and the technical flaws in Gauff's forehand, a wing that opponents were openly targeting. Despite her youth, could Gauff have plateaued early?
Gauff has wasted little time in quieting the doubters. After a first-round exit at Wimbledon to Sofia Kenin, she got herself a new team, bringing Brad Gilbert and Pere Riba on board. The results showed quickly, with a first WTA 500 title in Washington -- and just two weeks later, a first WTA 1000 trophy in Cincinnati, a run that included a first win over Swiatek, 7-6(2), 3-6, 6-4 in the semifinals.
After winning 11 of her past 12 matches, Gauff comes into her home major, where she was a quarterfinalist last year, not as a youngster with potential but a legitimate contender for the title. She's thriving on this, talking at Media Day about her newfound confidence and excitement about going "a little bit into September, too," referencing the latter stages of the US Open.
First, Gauff has to navigate a tricky opener. Former World No.27 Laura Siegemund may have had to qualify this year, but her current No.121 ranking is more a reflection of the 35-year-old German's injury woes in recent years than her ability. Siegemund is a former US Open doubles champion whose wide repertoire makes her one of the most entertaining shotmakers on tour. She possesses 10 career Top 10 wins, and defeated Gauff 5-7, 6-2, 6-3 in their only previous meeting, in the 2020 Auckland second round.
Moreover, Siegemund is rounding into form after missing three months at the end of 2022. Last month, she reached her first final in six years -- and first of her career on hard courts -- in Warsaw.
Three more to watch on Day 1
 Elena Rybakina (KAZ) vs. Marta Kostyuk (UKR)
Since winning her fifth career title in Rome in May, Rybakina has found her momentum repeatedly stalled by health issues. Illness forced her to withdraw from Roland Garros, and affected her title defence at Wimbledon, where she fell in the quarterfinals to Ons Jabeur. After a gruelling run to the Montreal semifinals, she retired against Jasmine Paolini in the Cincinnati third round, citing multiple injuries.
Highlights: Kostyuk d. Rybakina, 2023 Adelaide 1 R2
Kostyuk is one of the toughest draws Rybakina could have received. The Ukrainian's all-court game has been coming into its own this year following a maiden title in Austin in March. She's won two straight matches against Top 10 opponents this summer, Maria Sakkari at Wimbledon and Caroline Garcia in Washington. And she's beaten Rybakina both times they've played: once at pro level, 6-7(5), 6-2, 6-3 in the second round of Adelaide 1 this January, but also 6-1, 7-5 in the 2017 Australian Open junior semifinals.
Sloane Stephens (USA) vs.  Beatriz Haddad Maia (BRA)
One of the hardest first-round ties to call. Former US Open champion Stephens has been up-and-down throughout the summer: excellent performances to defeat Caroline Garcia in Cincinnati and Mirra Andreeva in Cleveland were reminders of her vintage form, but were both followed by low-intensity losses to Marketa Vondrousova and Sara Sorribes Tormo.
Haddad Maia enjoyed a phenomenal spring, becoming the first Brazilian in the Open Era to reach a Grand Slam semifinal at Roland Garros and then cracking the Top 10 for the first time. But a back injury forced her to retire against Elena Rybakina at Wimbledon, and she's won just one of three matches on the North American hard courts this month -- though, strictly speaking, three-set defeats to Leylah Fernandez in Montreal and to Karolina Muchova in Cincinnati can hardly be called poor losses.
Haddad Maia won the pair's only previous meeting 6-3, 6-3 in the second round of Acapulco 2019.
 Iga Swiatek (POL) vs. Rebecca Peterson (SWE)
Once again, Swiatek's World No.1 ranking is on the line at a Grand Slam. The defending champion needs to keep one round ahead of Aryna Sabalenka to stay at the summit, and she'll begin that quest against No.86-ranked Peterson.
The Swede enjoyed a strong first quarter, reaching her first final in four years in Merida, but has compiled just a 3-4 record over the past month at qualifying, ITF and WTA 125 level. Both of Swiatek's previous meetings with Peterson have also been in Grand Slams, and the Pole has dropped just six games in two matches to date at Roland Garros 2021 and the Australian Open 2022.
Also in action
Two-time US Open finalist Caroline Wozniacki, contesting the third event of her comeback from maternity leave, takes on 19-year-old qualifier Tatiana Prozorova. Former World No.1 Wozniacki has won one match in two tournaments so far this summer, while Prozorova will be playing the first Grand Slam main draw of her career.
Should Wozniacki win, she could face old rival and No.11 seed Petra Kvitova for the 15th time. Miami champion Kvitova takes on No.65-ranked Cristina Bucsa in a first-time encounter.
The 16-year-old sensation Mirra Andreeva stretched Gauff to three sets when they met in the Roland Garros third round in June. Now ranked No.63, Andreeva takes on Australian qualifier Olivia Gadecki for a chance to play Gauff again in the second round.
Former Australian Open finalist Danielle Collins has been resurgent this summer, scoring wins over Elina Svitolina, Maria Sakkari and Leylah Fernandez to reach the Montreal quarterfinals. The American will be seeking to reverse a 6-3, 6-4 loss to 18-year-old Linda Fruhvirtova in Dubai this February. Fruhvirtova, for her part, will bid to snap a six-match losing streak.
No.20 seed Jelena Ostapenko faces a tough opener against Italy's Jasmine Paolini, who reached her third career final -- and first on home soil -- in Palermo in July, and brought that form to the hard courts to make her first WTA 1000 quarterfinal in Cincinnati. Paolini won their only previous meeting all the way back in 2014, triumphing 6-4, 6-4 in Burnie ITF W50 qualifying.