NEW YORK (AP)—Monica Niculescu upset 27th-seeded Lucie Safarova in straight sets Friday at the U.S. Open to reach the fourth round of a Grand Slam for the first time.

The 68th-ranked Niculescu won 6-0, 6-1 to become the first Romanian woman to make the round of 16 at Flushing Meadows since Irina Spirlea in 1998. She had lost in the first round in her previous three appearances here.

Safarova had to repeatedly come back from deficits to beat Madison Keys in three sets in her last match. The Czech has never been past the third round at the U.S. Open.

It’s been a stellar tournament for the Romanian women, who knocked out the French Open and Wimbledon champs in the first round. Alexandra Dulgheru defeated fifth-seeded Petra Kvitova, while Simona Halep beat sixth-seeded Li Na.

Niculescu then eliminated Dulgheru in the second round.