World number one Iga Swiatek demolished "best friend" Kaja Juvan in straight sets on Friday to march into the last 16 at the US Open. Swiatek, who has been a close friend of Juvan since her youth tennis playing days, showed no mercy to the Slovenian world No.145 with a 6-0, 6-1 victory on the Louis Armstrong Stadium. "For sure I didn't like the fact I was winning with my best friend," Swiatek said afterwards. "It was like playing against a sister because I've known her for so long. "I don't have many friends but she's my best friend." The 49-minute drubbing sends defending champion Swiatek into a fourth-round meeting with either Latvian 20th seed Jelena Ostapenko or Bernarda Pera of the United States.