MASON, Ohio — Roger Federer didn't let a tricky wind blow him away.

The world's No. 1 player struggled in blustery conditions Thursday against a player he has dominated throughout his career. A 3-6, 6-3, 6-4 victory over Spain's David Ferrer put him in the quarterfinals of the Cincinnati Masters.

Federer took time off after his Wimbledon victory — his record 15th Grand Slam title — following the birth of his twin girls. His difficulties Thursday had everything to do with the wind, which got the stadium flags flapping furiously and played havoc with shots.

Federer had an uncharacteristic 35 unforced errors against Ferrer, who is 0-9 career against the Swiss star and has won only two sets in those matches.