Wimbledon champ Kvitova out at US Open

Novak Djokovic of Serbia reacts after defeating Sam Querrey (USA) on day six of the 2014 US Open tennis tournament at USTA Billie Jean King National Tennis Center, in New York, Aug 30, 2014. [Photo/Agencies]

The men's side, meanwhile, remained largely true to form. None of the top 10 and only two of the top 20 seeded men had lost entering Saturday.

The top-seeded Djokovic continued that trend with a routine 6-3, 6-2, 6-2 victory over American Sam Querrey, earning a spot in the round of 16 at a 22nd consecutive Grand Slam tournament. Djokovic counts the 2011 US Open among his seven major titles and has played in the past four finals at Flushing Meadows.

Third-seeded Stan Wawrinka, the Australian Open champion, got a welcome walkover into the fourth-round when his opponent, Blaz Kavcic, withdrew just before their scheduled match with a right foot injury.

Eighth-seeded Andy Murray needed four sets to get past Andrey Kuznetsov in humid, overcast conditions, his first day match since he battled cramps over much of his body in a first-round victory over Robin Haase. "I ate properly, I drank properly, I felt a lot better today," he said.

That sets up an intriguing fourth-round matchup with No 9 Jo-Wilfried Tsonga, who overcame tough winds in the Grandstand to beat Pablo Carreno Busta 6-4, 6-4, 6-4. His prediction: "I will come on the court as a fighter."

Tenth-seeded Kei Nishikori advanced in straight sets against No 23 Leonardo Mayer, and fifth-seeded Milos Raonic took three straight tiebreakers over Victor Estrella Burgos, who at 34 was the oldest man left in the draw.

In other key matches Saturday, American John Isner, seeded 13th, sought to defeat No 22 Philipp Kohlschreiber, the man who has beaten him in the third round the last two years.

Bouchard and 19-year-old Nick Kyrgios, a lanky Australian with a big serve who stunned Rafael Nadal in the fourth round at Wimbledon, are featured in the main night matches in Ashe.