World No. 1 Iga Swiatek moved into the fourth round of the U.S. Open, defeating her close friend Kaja Juvan of Slovenia 6-0, 6-1 on Friday in New York.

For Swiatek, the 49-minute match was her 10th straight win at the tournament. The defending champion, she is seeking her fifth Grand Slam title after winning the French Open earlier this year.

The 22-year-old from Poland was dominant on Friday, tallying 21 winners against five unforced errors. Juvan, on the other hand, hit just two winners and compiled 12 unforced errors.

“I didn’t like the fact I was kind of winning against my best friend,” Swiatek said in an on-court interview after the match. “Playing her is like playing a sister. … I don’t have many friends but she’s my best friend.”

Swiatek became the youngest woman to reach the Round of 16 for the third consecutive time since Caroline Wozniacki reached four straight from 2008 to 2011.

Next on the docket for Swiatek, with a berth in the quarterfinals on the line, is No. 20 seed Jelena Ostapenko of Latvia, a 4-6, 6-3, 6-3 winner over American Bernarda Pera.

Earlier Friday, No. 10 Karolina Muchova of the Czech Republic eliminated another American, Taylor Townsend, 7-6 (0), 6-3.

“The match was kind of what I expected. Tricky one,” Muchova said. “Taylor, I think, played really, really great from the start. The first set was very tough, very close. I’m glad I refocused very well for the tiebreak, and I think I played well there. As well, I felt start of the second set it was a little bit more in my hands.”

Waiting for Muchova in the fourth is unseeded Xinyu Wang of China, who defeated Slovakian Anna Karolina Schmiedlova 4-6, 6-3, 6-2. Wang converted five of 10 break opportunities and staved off nine of 11 on her serve.

–Field Level Media