HIGHLIGHTS-Tennis-U.S. Open day four

Playing in her first tournament in over three years following a maternity break, Pironkova won an overwhelming 93% of her first serve points, breaking the twice Grand Slam champion three times. Ons Jabeur of Tunisia, seeded 27th, beat Estonia's Kaia Kanepi 7-6(8) 6-0 to move into the third round.

Highlights of the fourth day at the U.S. Open in New York on Thursday. The Grand Slam is being played without spectators due to the COVID-19 pandemic. (Times ET; GMT-4): 1235 MUGURUZA UPSET BY UNSEEDED PIRONKOVA IN STRAIGHT SETS

Spain's 10th seed Garbine Muguruza was knocked out 7-5 6-3 by unranked Bulgarian Tsvetana Pironkova in the second round. Playing in her first tournament in over three years following a maternity break, Pironkova won an overwhelming 93% of her first serve points, breaking the twice Grand Slam champion three times.

Ons Jabeur of Tunisia, seeded 27th, beat Estonia's Kaia Kanepi 7-6(8) 6-0 to move into the third round. 1109 PLAY UNDERWAY AT FLUSHING MEADOWS

Play began in bright sunshine in New York with the temperature hovering around 26 degrees Celsius (78.8°F), with an expected high of 31 degrees. Day four begins with a battle between American teenagers Amanda Anisimova and Katrina Scott at the Louis Armstrong Stadium.

Australian Open champion Sofia Kenin, second seed Dominic Thiem, Serena Williams and Andy Murray are in action later on Thursday. READ MORE:

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Tsitsipas grinds down Cressy to reach third round (Compiled by Rohith Nair in Bengaluru, editing by Ed Osmond)