Iga Swiatek shrugged off lingering weariness to partner Casper Ruud to back-to-back victories in the revamped mixed doubles competition at the US Open on Tuesday.

Swiatek — who on Monday had battled through a two-hour tussle with Jasmine Paolini to win the Cincinnati Open — looked full of energy as she and Ruud powered into Wednesday’s semi-finals.

Swiatek and Ruud needed just 39 minutes to dispatch the US pairing of Madison Keys and Frances Tiafoe 4-1, 4-2 in their opening game at Arthur Ashe Stadium, and then reappeared roughly 20 minutes later to defeat Caty McNally and Lorenzo Musetti 5-3, 4-2 in their quarter-final clash.

The victories capped a gruelling 24 hours for Polish star Swiatek, who hot-footed it to the airport after Monday’s win in Cincinnati and only arrived at her hotel in New York in the early hours of Tuesday.

“Honestly the last two days have felt like one day, but I’m super happy to be here,” Swiatek said.

Ruud and Swiatek had just enough time to fit in a quick practice before taking to the court in their first match as a doubles pairing.

“I was happy to team up with Iga,” Ruud said afterwards.

“She’s on the winning train these days so I’m just jumping on the train and let’s see if we can win some more before the mixed doubles is over.

“I was super happy to team up with Iga — I think everyone should show some appreciation to Iga today. She only got to her hotel 12 hours ago at 2:30am, and she’s here playing.”

McNally and Musetti had progressed to the last eight earlier Tuesday after taking care of Naomi Osaka and Gael Monfils 5-3, 4-2.

In other early results on Tuesday, US tennis icon Venus Williams and partner Reilly Opelka exited against Karolina Muchova and Andrey Rublev, losing 4-2, 5-4.

Italy’s reigning champions Andrea Vavassori and Sara Errani ousted second seeds Elena Rybakina and Taylor Fritz 4-2, 4-2.

Earlier on Tuesday, world number one Jannik Sinner’s withdrawal from the mixed doubles was confirmed as expected.

Sinner, who retired due to illness in the first set of his Cincinnati Open final with Carlos Alcaraz on Monday, was due to partner Katerina Siniakova in the doubles.

Sinner and Siniakova were replaced in the draw by the American duo of Danielle Collins and Christian Harrison.

This year’s US Open mixed doubles competition is being held over Tuesday and Wednesday in the week before the main singles draws get under way.

The tournament is using a modified scoring system, with short sets to four games, no-advantage scoring, tiebreakers at four-all and a 10-point match tiebreak in lieu of a third set.

The final will be a best-of-three set match to six games, featuring no-advantage scoring, with tiebreakers at six-all and a 10-point match tiebreaker instead of a third set, with the winning pairing pocketing $1 million.