Australian Nick Kyrgios blasted 15 aces to blow past Japan's Yoshihito Nishioka 6-2 7-5 on Thursday and reach the quarterfinals at the Citi Open in Washington, D.C. Kyrgios was dominant on serve as he enjoyed his least stressful match of the tournament thus far. He was broken on service just once by Nishioka and won 85 percent of his first serves. Playing in his first tournament since his testy second round loss to Rafa Nadal at Wimbledon, Kyrgios will next face unseeded Slovakian Norbert Gombos. Top-seeded Stefanos Tsitsipas of Greece overcame an uneven performance to take down Australian Jordan Thompson 6-3 7-6(4). Tsitsipas trailed 5-4 in the second set but climbed out with some timely serves to ultimately prevail. "I made a lot of unforced errors in those break points, and getting to those break points, I played fantastic," Tsitsipas told the Washington Post. "I played very brave and very smart, and suddenly I start thinking about it a bit too much, and that's what happens. I make mistakes." The 20-year-old Tsitsipas, who owns wins over both Roger Federer and Nadal this year, will now take on Frenchman Benoit Paire who outmatched fifth-seeded American John Isner 7-6(3) 6-3. The 10th-seeded Paire matched Isner's hard-hitting serve and produced 12 aces to Isner's 14. Eighth seed Milos Raonic was upset by German Peter Gojowczyk 6-4 6-4, while Marin Cilic beat 18-year-old Canadian Felix Auger-Aliassime 6-3 6-4. Auger-Aliassime made 11 double faults in the defeat. "I couldn't figure it out, and it was just really tough out there today," Auger-Aliassime said. "Today has shown that I need to improve a lot of things still." On the women's side, 17-year-old Catherine McNally fought through chest congestion and fatigue from also playing doubles to advance to her first ever quarter-final with a 6-3 1-6 6-3 win over Christina McHale. "I haven't gone to bed – the past few nights I got to bed at like 1 a.m. because of doubles," McNally said. "For me, I think it just is a reality of what the tour is like." In other action, Camila Giorgi beat Rebecca Peterson 3-6 6-3 6-4 to set up a quarterfinal match up with Zarina Diyas who upset fifth seed Lesia Tsurenko 6-4 6-4. Fourth seed Su-Wei Hsieh squeezed past Varvara Gracheva 7-5 4-6 7-6(6).