The top seed in both the men's and women's draw faced significant challenges on Tuesday.

Jannik Sinner erased a rough first set, in which he won just two games, by limiting his opponent to just five games in the final three sets.

Iga Swiatek, the top seed in the women's draw, was on the verge of playing a third and deciding set before erasing all three of her opponent's set-point opportunities in the second set.

Tuesday also proved that Naomi Osaka is still an incredibly difficult player to defeat at the US Open.

The two-time U.S. Open champion defeated No. 10 seed Jelena Ostapenko in straight sets, earning her first top ten win in more than four and a half years.

Here are the top results and most noteworthy reactions from Tuesday's play.

Tuesday U.S. Open Results

Men's Singles

No. 1 Jannik Sinner def. Mackenzie McDonald, 2-6, 6-2, 6-1, 6-2

No. 3 Carlos Alcaraz def. Li Tu, 6-2, 4-6, 6-3, 6-1

No. 5 Daniil Medvedev def. Dusan Lajovic, 6-3, 3-6, 6-3, 6-1

No. 7 Hubert Hurkacz def. Timofey Skatov, 6-3, 7-6(4), 7-6(3)

No. 10 Alex de Minaur def. Marcos Giron, 6-3, 6-4, 5-7, 6-4

Thanasi Kokkinakis def. No. 11 Stefanos Tsitsipas, 7-6(5), 4-6, 6-3, 7-5

No. 14 Tommy Paul def. Lorenzo Sonego, 6-4, 6-2, 5-7, 6-2

No. 16 Sebastian Korda def. Corentin Moutet, 7-6(3), 6-1, 6-0

Jakub Mensik def. No. 19 Felix Auger-Aliassime, 6-2, 6-4, 6-2

David Goffin def. No. 22 Alejandro Table, 7-6(7), 6-1, 7-5

Daniel Evans def. No. 23 Karen Khachanov, 6-7(7), 7-6(2), 7-6(4), 4-6, 6-4

No. 24 Arthur Fils def. Learner Tien, 6-4, 2-6, 6-1, 6-2

No. 25 Jack Draper def. Zhizhen Zhang, 6-3, 6-0, 4-0 (retired)

Christopher O'Connell def. No. 26 Nicolas Jarry, 6-4, 6-3, 4-6, 6-3

No. 30 Matteo Arnaldi def. Zachary Svajda, 6-3, 6-2, 6-2

No. 31 Flavio Cobolli def. James Duckworth, 6-1, 4-6, 6-4, 6-4

Women's Singles

No. 1 Iga Swiatek def. Kamilla Rakhimova, 6-4, 7-6(6)

No. 4 Elena Rybakina def. Destanee Aiava, 6-1, 7-6(1)

No. 5 Jasmine Paolini def. Bianca Andreescu, 6-7(5), 6-2, 6-4

No. 6 Jessica Pegula def. Shelby Rogers, 6-4, 6-3

Naomi Osaka def. No. 10 Jelena Ostapenko, 6-3, 6-2

Caroline Dolehide def. No. 11 Danielle Collins, 1-6, 7-5, 6-4

No. 15 Anna Kalinskaya def. Lauren Davis, 6-2, 6-2

No. 16 Liudmila Samsonova def. Qiang Wang, 6-2, 7-5

No. 18 Diana Shnaider def. Nadia Podoroska, 6-0, 6-1

No. 21 Mirra Andreeva def. Camila Osorio, 6-2, 7-6(4)

No. 22 Beatriz Haddad Maia def. Elina Avanesyan, 4-6, 6-0, 6-2

Anastasia Potapova def. No. 23 Leylah Fernandez, 2-6, 6-4, 7-5

No. 25 Anastasia Pavlyuchenkova def. Taylah Preston, 6-2, 6-0

Renata Zarazua def. No. 28 Caroline Garcia, 6-1, 6-4

No. 30 Yulia Putintseva def. Linda Noskova, 7-6(3), 6-4

No. 31 Katie Boulter def. Aliaksandra Sasnovich, 5-7, 6-2, 6-2

Jannik Sinner Sluggish Early, Dominant Late

Jannik Sinner got off to a rough start against American Mackenzie McDonald.

The top-seeded Italian won just 53% of points on his first serve and committed 14 unforced errors, quickly falling down a set.

Sinner's inconsistent play persisted into the second set, resulting in an immediate break on his serve.

Despite trailing by a set-and-serve break, the Italian found an incredible groove and began to dominate.

Most impressively was a third set, where he won 17 of 18 points on serve without committing a single unenforced error.

The 23-year-old remains a firm contender to win it all, along with tournament favorite Carlos Alcaraz, who defeated Li Tu in four sets.

Barring something unexpected, another Alcaraz-Sinner U.S. Open match appears to be in the works.

Iga Swiatek Struggles in Opening Round Victory

Kamilla Rakhimova, a "lucky loser," put top seed Iga Swiatek to the test in her first round match.

In their second set tiebreaker, the five-time Grand Slam champion nearly forced a third set before denying Rakhimova three-set point opportunities.

Swiatek struggled immensely throughout the match, committing 41 unforced errors—an unusually high mark in a two-set match by her standards.

Despite her difficulties against Rakhimova, the Pole should encounter very few obstacles before possibly facing Mirra Andreeva in the fourth round.

Andreeva, just 17 years old, has already defeated four top ten players this year and is more than capable of holding her own against the Pole, as evident by their recent Cincinnati Open match, which Swiatek narrowly escaped in three sets.

Naomi Osaka Impresses in U.S. Open Return

Naomi Osaka continues to look in top form.

The two-time U.S. Open champion, who was on maternity leave in 2023, defeated No. 10 seed Jelena Ostapenko, earning her first top ten win in four and a half years.

The former World No. 1 committed just five errors in total while winning 80% of points on her first serve.

Osaka faces a tough task in the second round, pitted up against 2023 U.S. Open semifinalist Karolina Muchova.

However, if she's able to play anything like she did today, it'll be incredibly tough to picture her losing.