Belinda Bencic, of Switzerland, returns the ball to  Lucie Safarova, of the Czech Republic, during a match at the Western & Southern Open tennis tournament, Thursday, Aug. 20, 2015, in Mason, Ohio. (AP Photo/John Minchillo)"

Belinda Bencic, of Switzerland, returns the ball to Lucie Safarova, of the Czech Republic, during a match at the Western & Southern Open tennis tournament, Thursday, Aug. 20, 2015, in Mason, Ohio. (AP Photo/John Minchillo)"


Lucie Safarova, of the Czech Republic, returns the ball to Belinda Bencic, of Switzerland, during a match at the Western & Southern Open tennis tournament, Thursday, Aug. 20, 2015, in Mason, Ohio. (AP Photo/John Minchillo)"


MASON, Ohio (AP) — Belinda Bencic has withdrawn from the Western & Southern Open after dropping the first set against seventh-seeded Lucie Safarova 6-2 in the round of 16.

No reason was immediately given for the 12th-seeded Bencic’s abrupt withdrawal Thursday.

The Swiss teenager was coming off the biggest moment of her brief career, when she won the tournament in Toronto last week and upset top-ranked Serena Williams in the semifinals.

Safarova will meet either 14th-seeded Elina Svitolina or unseeded Caroline Garcia in the quarterfinals at Cincinnati.

Belinda Bencic, of Switzerland, returns the ball to Lucie Safarova, of the Czech Republic, during a match at the Western & Southern Open tennis tournament, Thursday, Aug. 20, 2015, in Mason, Ohio. (AP Photo/John Minchillo)"
http://aimmedianetwork.com/wp-content/uploads/sites/22/2015/08/web1_105334443-907139a878ff46579eaf6d08d98c9c4c.jpgBelinda Bencic, of Switzerland, returns the ball to Lucie Safarova, of the Czech Republic, during a match at the Western & Southern Open tennis tournament, Thursday, Aug. 20, 2015, in Mason, Ohio. (AP Photo/John Minchillo)"

Lucie Safarova, of the Czech Republic, returns the ball to Belinda Bencic, of Switzerland, during a match at the Western & Southern Open tennis tournament, Thursday, Aug. 20, 2015, in Mason, Ohio. (AP Photo/John Minchillo)"
http://aimmedianetwork.com/wp-content/uploads/sites/22/2015/08/web1_105334443-63513706f830468797be49c7993c86d7.jpgLucie Safarova, of the Czech Republic, returns the ball to Belinda Bencic, of Switzerland, during a match at the Western & Southern Open tennis tournament, Thursday, Aug. 20, 2015, in Mason, Ohio. (AP Photo/John Minchillo)"