Naomi Osaka def. Angelique Kerber (6)

Defending champion Kerber came into the US Open without a Top 20 win on her 2017 resume and just one finals appearance (in Monterrey). But few people gave the 45th-ranked Osaka much of a chance at a first-round upset in New York. Not only did Osaka beat the reigning champ and former world No. 1, but she did so emphatically, with a 6-3, 6-1 drubbing that took just a little over an hour inside Arthur Ashe Stadium. Osaka, making her second appearance in the Big Apple, went on to reach the third round, where she lost to eventual quarterfinalist Kaia Kanepi.

play video Kerber vs. Osaka

Aleksandra Krunic def. Johanna Konta (7)

Down a set to No. 7 seed Konta, 24-year-old Krunic looked down and almost out in her first-round match inside the Grandstand. But the scrappy Serb clawed her way back into contention behind an unconventional game of slices, short angles and looped ground strokes. The Brit began mis-firing from the baseline and seemed reluctant to go to a Plan B when the errors began piling up. That’s when the No.78 player in the world seemed the more composed of the two, content to chase down balls, change speeds from the baseline and let the Wimbledon semifinalist punch herself out. Konta was among the pre-tournament favorites, but her stay was a short one as she crashed out 4-6, 6-3, 6-4.

play video Konta vs. Krunic

Denis Shapovalov def. Jo-Wilfried Tsonga (8)

One of the biggest stories of Week 1 was the surprise run of Canadian teen Shapovalov, who was thrust into the limelight in August when he upset Rafael Nadal in Montreal. He jumped 74 places in the rankings to No. 69 after the entry cut-off, meaning he did not gain direct entry to the main draw. After winning three qualifying matches in Flushing Meadows, Shapovalov was trending upward, and he didn’t stop with a first-round win over Daniil Medvedev. In his first-ever match inside Arthur Ashe Stadium, in his second-ever Grand Slam, the 18-year-old toppled eighth-seeded Tsonga in straight sets, 6-4, 6-4, 7-6. It was only his third career win over a Top 20 player, but his second in the space of three weeks.

play video Shapovalov vs. Tsonga

Maria Sharapova def. Simona Halep (2)

On paper, this wouldn’t usually be considered a huge upset – a five-time Grand Slam champion and former world No. 1 beating a two-time major finalist who had reached at least the quarterfinals in each of her past two trips to the US Open. But what made this first-round match intriguing was that Sharapova was playing in just her fifth tournament, and 10th match, in 20 months. It was her first Grand Slam match since the 2016 Australian Open and her first US Open appearance since losing in the fourth round in 2014. Sharapova shook off the rust and hit through Halep, advancing with a 6-4, 4-6, 6-3 victory before dropping to her knees inside Arthur Ashe Stadium in a rare show of emotion. Unseeded in New York, Sharapova could have been drawn against any of the other 127 women in the draw. The fact she took out the world No. 2 on Day 1 in prime time was a remarkable start to the competition.

play video Halep vs. Sharapova

Borna Coric def. Alexander Zverev (4)

Zverev was one of the trendy picks to win the US Open this year in a men’s draw decimated by injuries and lacking some of the firepower of years past. With his flowing locks and throwback-style pinstriped shirt, Zverev caught the eye of fans and pundits with both his game and appearance. But in a battle of 20-year-old Next Generation stars, it was the Croat who had the Grandstand crowd on its feet after rallying to a 3-6, 7-5, 7-6, 7-6 victory in a three-and-a-half hour thriller. Coric, the No. 61-ranked player in the world, had not been past the first round in his past two US Opens, but after showing the kind of form he displayed to beat Andy Murray and Dominic Thiem earlier in the year, he battled his way into Round 3. 

play video Coric vs. Zverev