AFP Sport looks at three matches to watch on day two of 2024's final Grand Slam, which will conclude on September 8th.
Jannik Sinner v Mackenzie McDonald
Australian Open champion Sinner plays his first match since it emerged he had twice tested positive for a banned substance but had escaped a lengthy ban.
The 23-year-old was cleared of any wrongdoing over the presence of the anabolic agent clostebol after it was ruled he had been inadvertently contaminated by his physio, who had used a spray to treat a cut to his own hand.
"In my mind I know that I haven't done anything wrong," said Sinner.
On Tuesday, the Italian faces 140th-ranked McDonald, who has never been past the second round at Flushing Meadows but who defeated a stricken Rafael Nadal at the Australian Open last year.
Sinner has endured a rollercoaster relationship with the US Open.
Twelve months ago, he was defeated in five sets by Alexander Zverev in the last 16 while in 2022 he was knocked out by Carlos Alcaraz in a five-set quarter-final which finished just before 03:00.
Sinner boasts a 3-0 head-to-head record with the 29-year-old McDonald.
Carlos Alcaraz v Li Tu
The 21-year-old Alcaraz won the first of his four Grand Slam titles in New York in 2022 before going on to become the youngest world number one.
The Spaniard has since added Wimbledon in 2023 before claiming the French Open and successfully defending his Wimbledon title in July by sweeping past Novak Djokovic in the final.
A tearful Alcaraz, however, was defeated by Djokovic in the Olympic final in Paris earlier this month and has played just once since, losing his opening match in Montreal to French veteran Gael Monfils.
Li, ranked 186 in the world and who came through qualifying to reach the US Open main draw for the first time, hasn't won a match on the main tour in 2024.
However, his clash against Alcaraz will be emotional as the tournament falls on the second anniversary of the death from cancer of his mother, Yu Ping Zheng.
"She was the one that made sure food was on the table, that I was wearing my sunscreen, that I got enough sleep, things like that, mom's stuff," the 28-year-old said.
Jelena Ostapenko v Naomi Osaka
Two-time US Open champion Osaka missed last year's US Open after giving birth to her daughter Shai and the former world number one's return to the sport has yet to hit top gear.
She has made two quarter-finals at tour events in 2024 but hasn't progressed beyond the second round at the majors.
Osaka at least showed she can still live with the best as she showed by holding a match point against world number one Iga Swiatek at the French Open.
On Tuesday, the 26-year-old former world number one, now ranked 88, tackles 2017 French Open champion Ostapenko.
"She's honestly one of my favourite players to watch. I think we are polar opposites in a way," said Osaka.
"I respect her a lot. She was the first player in our generation to win a Grand Slam. She's a champion. I'm really looking forward to it."
The 10th-ranked Ostapenko enjoyed her best run at the US Open in 2023 where she lost to eventual champion Coco Gauff.
The pair have only ever met once, back in 2016 at the French Open when Osaka came out on top in straight sets.
