Iga Swiatek routs 'sister' Kaja Juvan to reach last 16 at US Open
Swiatek grew up with Juvan through the junior ranks and the two dined together earlier this week but for 49 minutes in Louis Armstrong Stadium their friendship was put on hold while the top-seeded Pole got down to business.
"For sure I didn't like the fact that I was winning with my best friend. But I knew that I had to be really focused and not let myself think about that because it was really like playing against a sister," said Swiatek.
"I don't have many friends but she's my best friend. So yeah, that was the toughest part for sure."
Up next for Swiatek will be Latvian 20th seed Jelena Ostapenko, a 4-6, 6-3, 6-3 winner over American Bernarda Pera.
Swiatek was in total control from the start, dominating all aspects of the match throughout a one-sided opening set during which she dropped just three points on serve and converted all three of her break points.
It was more one-way traffic in the second as Swiatek won the first 11 points en route to a 3-0 lead before Juvan finally got on the board after 40 minutes with a hold following which the world number 145 smiled and playfully raised her arms in triumph.
But the moment was short-lived for Juvan as Swiatek restored order with a hold to love and then another break before closing out the match with another routine service hold before the two players shared a warm embrace at the net.
Swiatek, who must go at least one round further than Aryna Sabalenka to hang onto the world number one ranking she has held since April 2022, has been near flawless in New York having dropped just nine games through three rounds.
The Pole arrived in New York with her sights set on becoming the first woman to retain a US Open crown since Serena Williams won three straight titles from 2012-14 and has yet to offer anyone a reason to doubt her prospects.
Despite all her success, Swiatek admitted she was still coming to terms with her lofty position atop the women's game.
"Honestly, I kind of have to learn how to find more joy in that," she said. "I talked to Roger (Federer) about that last week and the best way to approach it is really embrace it and really be proud and happy with your results."
