Wonderful from Sabalenka. She pummels Osorio’s second serve before advancing to the net, a deft forehand toying with her opponent. And, just like that, she’s broken back. Sabalenka goes 5-2 up and is serving for the first set.

Sabalenka is cruising, breaking for the second time to go 4-1 up against Osorio. The defending champion is angry with herself, though, after a backhand finds the net. An ace swiftly follows but Sabalenka’s balance is off with her backhand – Osorio has two break points. Sabalenka stays calm at the net to save the first with a forehand smash but then double-faults! Osorio has the break; Sabalenka leads 4-2.

Arthur Fils has taken the first set against Stefanos Tsitsipas 6-4, while Karolina Muchova is sprinting to the second round – she’s up 6-3, 5-0 against Sinja Kraus.

Osorio finds some confidence with a couple of crushing winners before Sabalenka saves a break point with an ace. Sabalenka’s serves down the middle do the job as she goes 3-1 up in the first set.

Sabalenka fires a backhand to take Osorio to deuce. Osorio double-faults once again before showing off a steely defence against her opponent’s phenomenal power, with Sabalenka eventually pummelling the net. But Osorio serves consecutive double faults – that’s five in the match – to gift Sabalenka the break. The world No 1 goes 2-1 up.

Sabalenka eases through on her serve, advancing to the net to secure her first game of the tournament with a forehand volley. It’s 1-1 in the opening set against Osorio.

Sabalenka and Osorio are underway on Arthur Ashe, with the Colombian serving. She records two double-faults before Sabalenka seizes upon the second serve, whipping a blistering forehand to make it deuce. But the defending champion finds the net and the stratosphere, too, as Osorio holds to go 1-0 up.

Back to Tsitsipas v Fils, and the latter has the chance to break … he goes long with a backhand and we’re back to deuce, with Fils leading the first set 3-2. Tsitsipas pushes forward to swat a forehand winner and a big serve gives him the game. 3-3 it is.

Britain’s Harriet Dart is up against Peyton Stearns, who plays a deft backhand volley to hold her serve and go 2-1 up. Over on Grandstand Karolina Muchova, runner-up at Wimbledon this year and seventh seed here, is leading 4-1 against Sinja Kraus.

Fils, the 10th seed, finds himself stuck on deuce while serving against Tsitsipas – but the Frenchman saves three break points before a backhand down the line gives him the opening game.

Arthur Fils, who claimed his first Masters title this month by beating Frances Tiafoe in Cincinnati, has an intriguing opening clash. He’s up against two-time grand slam finalist Stefanos Tsitsipas on Louis Armstrong.

Here’s more on Sabalenka by Tumaini:

Such is the competition at the top of women’s tennis, her rivals are congregating at her front door. Elena Rybakina begins this tournament sitting at No 1 in the live standings and in control of her own destiny. Sabalenka must win the title to have any hope of retaining the top ranking, but Rybakina will become the new No 1 regardless of all other results if she reaches the semi-finals. Should either Coco Gauff or Jessica Pegula win the title and Rybakina fails to make the semi-finals, they would take top spot. This additional pressure could further add to Sabalenka’s woes, but perhaps, after 97 consecutive weeks as the undisputed best player in the world, this is exactly what she needs.

Aryna Sabalenka will be up on Arthur Ashe at 11.30am EDT (4.30pm BST). She’s met Camila Osorio twice, winning in straight sets on both occasions, the first of those at Wimbledon in 2021. The world No 1 is the defending champion and triumphed in 2024 too – but she’s had a tough time of it recently. Sabalenka lost in the round of 16 at the Cincinnati Open to Sara Bejlek and hasn’t reach a final since winning the Miami Open in March. Maybe a return to New York, where she’s had so much success, will bring the rhythm back.

A 12.13am start! It’s a no from me.