Aryna Sabalenka's bid for a rare US Open three-peat got off to a winning start Monday as she dispatched Camila Osorio, while French rising star Arthur Fils suffered a surprise loss.
World number one Sabalenka shook off her recent lackluster form to beat Colombia's Osario 6-2, 6-4, in the Belarusian's opening match at New York.
"I feel like this is one of my favorite stadiums," Sabalenka said at the giant Arthur Ashe venue in Flushing Meadows, where she has won two of her four Grand Slams.
Sabalenka has not won a tournament since her victory in the Miami Open in March, and was bundled out of Wimbledon in the fourth round by Naomi Osaka.
But she looked comfortable for most of her opener, landing several of her thunderous groundstrokes to see off her counter-punching opponent.
The double title defense is on.
— US Open Tennis (@usopen) August 31, 2026
Aryna Sabalenka defeats Osorio 6-2, 6-4! pic.twitter.com/qcIwgotKHI
On the men's side, recent Cincinnati Masters champion Fils suffered disappointment, losing his opening match to Greece's Stefanos Tsitsipas.
Fils, 22, entered the contest with the highest expectations of his career, having this month become the first French player to win a Masters 1000 in over a decade.
The Frenchman had won all five of his previous encounters with Tsitsipas.
But Fils, ranked 11th, fell to Tsitsipas 4-6, 7-6 (7/3), 6-1, 6-4.
"I am speechless, I don't know what to say," said Tsitsipas, a former top five player who has slumped to 53 in the world.
"It's an amazing start to the tournament."
The US Open got off to a dramatic opening day Sunday, as ailing Novak Djokovic suffered his earliest Grand Slam exit in 20 years, falling in five brutal sets to Mariano Navone.
The 39-year-old was reduced to tears by a crowd trying to will him to victory, but his physical distress left him powerless, and has thrown his Grand Slam future into doubt.
Djokovic's elimination makes an already wide-open men's draw even more intriguing -- Jannik Sinner is absent with a bad knee, while Carlos Alcaraz is only just returning from a four-month injury layoff.
Carlos Alcaraz opened his US Open title defence in solid fashion, defeating Russia's Roman Safiullin in straight sets in his highly anticipated first singles match in more than four months.
Executing a game plan of controlled aggression, the Spaniard defeated Safiullin, 6-4, 6-4, 6-4. Alcaraz revealed no lingering effects from a wrist injury that kept him out of the last two Grand Slams.
Top-seeded German Alexander Zverev will play his first match against Italy's Lorenzo Sonego on Tuesday.
Before that, Monday's US Open action will feature veteran wild card Stan Wawrinka, in what could be his last Grand Slam match, as well as US hopefuls Ben Shelton and Frances Tiafoe.
Osaka will face Anastasia Zakharova in the Arthur Ashe Stadium's night session, while Iga Swiatek takes on China's Wang Xiyu.
Earlier on Monday, this year's Wimbledon finalist Karolina Muchova beat Sinja Kraus 6-3, 6-0, and Qinwen Zheng came back from a set down to defeat Kristina Liutova 4-6, 6-3, 6-1.