Iga Swiatek began her US Open title defence with an emphatic first-round victory as eighth seed Maria Sakkari fell to a surprising loss.

Sakkari had a day to forget on Court 17 as she was knocked out by world number 71 Rebeka Masarova of Spain.

The Greek had been 4-1 up in the first set but Masarova responded in thrilling fashion to claim a 6-4 6-4 win.

Swiatek has won both previous meetings with world number 86 Peterson and came through this encounter on Arthur Ashe Stadium in imperious style..

The 22-year-old Pole, who is bidding to win her fifth Grand Slam title, will face Daria Saville of Australia in the second round.

Swiatek said: "I wanted to start the tournament with everything I was focusing on. I was happy to play a great game, with all the pressure and expectations, I was happy on the court.

"I feel like everything that is going on around us is taking away our attention and what we want to achieve with our games and careers.

"I want to remind myself that I want to develop as a player. The numbers and stats don't really matter to me. I'm just trying to focus on my performance."

There were routine wins for other seeded players on the opening day.

Victoria Azarenka made light work of Frenchwoman Fiona Ferro in their match at the Louis Armstrong Stadium.

The 18th seed, who reached the US Open final in 2012, 2013 and 2020, wrapped up a comprehensive 6-1 6-2 victory over the world 190.

Elsewhere, Czech 10th seed Karolina Muchova clinched a 6-4 6-0 win over Storm Sanders of Australia, while 15th seed Belinda Bencic of Switzerland eased passed Kamilla Rakhimova 6-2 6-4.