Lucie Safarova will face either 14th-seeded Elina Svitolina or unseeded Caroline Garcia in the quarter-finals of the Cincinnati Open following Belinda Bencic's withdrawal after one set today.
No reason was immediately given for the Swiss teenager's withdrawal after losing the first set 6-2 to the Czech world number six.
Bencic began the match by breaking Safarova's serve in the first but was unable to capitalise as the Czech broke back immediately.
Safarova went on to break Bencic's serve a further two times to win the first set 6-2, after which the Swiss retired from the match.