The first round draw between No.2 seed Simona Halep and wildcard former champion Maria Sharapova sent shockwaves through the tennis world. Between them, they have only one first-round exit at the US Open - Halep's debut, in 2010, which she lost to No.4 seed Jelena Jankovic in three sets.
In total, Halep has fallen at the first hurdle in a Slam 10 times. Sharapova, on the other hand, has suffered only three first-round Slam losses in a 14-year career, two of which came in her first two majors in 2003. The Russian's last first-round exit at a Slam was at the hands of Maria Kirilenko at the 2010 Australian Open.
Sharapova leads the head-to-head against Halep 6-0 - however, three of those matches were tight three-setters, including the 2014 Roland Garros final, and the Russian has only once won a set against the Romanian by an easier score than 6-3.
No.13 seed and former World No.2 Petra Kvitova will take on former World No.1 and 2008 US Open finalist Jelena Jankovic in another of the first day's popcorn matches. Kvitova leads the head-to-head 4-3, but they have not played since the third round of Wimbledon 2015, when Jankovic upset the defending champion in three sets.
Caroline Wozniacki is bidding for her 100th Slam main-draw victory today against qualifier Mihaela Buzarnescu. The No.5 seed would become just the 10th active player to reach that milestone. Over one-third of the Dane's 99 wins to date have come at the US Open.
Following last year's Rio Olympics, former World No.11 Sloane Stephens was forced to miss 11 months due to surgery on her right foot; her ranking sank to No.957 at the end of July. Just four tournaments into her comeback, though, back-to-back Premier 5 semifinals in Toronto and Cincinnati sent the American's ranking skyrocketing 850 spots in two weeks - and she's already firmly back in the Top 100 at No.83.
No.7 seed Johanna Konta faces a potentially tricky first-round encounter against Aleksandra Krunic. The Serb may have lost in the first round in seven of her nine Slam main draws, but one of the exceptions was her breakthrough at the 2014 US Open, at which she felled Madison Keys and Petra Kvitova en route to the second week. And Krunic indicated that her giant-killing form may have returned this month: a fortnight ago, she took down Roland Garros champion Jelena Ostapenko in Cincinnati.
Last July, Lauren Davis began a surge that would see her make three WTA finals, win her maiden title in Auckland and reach a career high of No.26 in May. However, the No.32 seed is yet to win a Slam match in 2017 - and is coming into her home Slam off five straight first-round defeats. She'll have a chance to rectify that against wildcard Sofia Kenin.
Last September, Misa Eguchi was two points away from her biggest career title in the Dalian WTA 125 event when she suffered a left knee injury that would force her not only to retire from that final - but to undergo surgery and sit out for nine months. However, her protected ranking has enabled her to make her Slam debut as the last player accepted into the main draw - and by a twist of fate, she'll play Kristyna Pliskova in the first round - the woman she last faced in that unfortunate Dalian final nearly a year ago.
Thirteen women will be playing their first Slam main draw at this year's US Open, six of whom are in action today: joining Eguchi are qualifiers Viktoria Kuzmova, Mihaela Buzarnescu, Claire Liu, Tereza Martincova and Anna Zaja. It's the highest number of debutantes since the 2006 Australian Open's cohort of 13, which included several names that have become very familiar: Akgul Amanmuradova, Victoria Azarenka, Lauren Breadmore, Lourdes Domínguez Lino, Jarmila Gajdosova (now Wolfe), Tsvetana Pironkova, Olga Savchuk, Hana Sromova, Elena Vesnina, Galina Voskoboeva, Kathrin Woerle, Yan Zi and Yuan Meng.
No.18 seed Caroline Garcia is having her best Slam season to date: having fallen before the second week in her first 20 Slams, she made the quarterfinals at Roland Garros and backed it up with a fourth-round showing at Wimbledon. However, her opponent today, debutante Tereza Martincova, was the victor in their last match - just over a month ago in the second round of Gstaad.
The pundits are divided on the most intriguing first-round encounter, Simona Halep against Maria Sharapova: Kelyn Soong at the Washington Post favours the Russian's head-to-head advantage, but Mike Dickson at the Daily Mail believes Sharapova will need the No.2 seed to underperform.
Get to know two of the US Open qualifiers with the most compelling back stories - cancer survivor Allie Kiick and 2015 junior Wimbledon champion Sofya Zhuk - in our WTA Insider interviews.
Practice makes perfect - see how some of the top players in action today have been preparing for their US Open campaigns.