NEW YORK Aug 28 (Reuters) - Former world number one Ana Ivanovic was upset 7-5 6-4 by 42nd-ranked Karolina Pliskova of the Czech Republic in the second round of the U.S. Open on Thursday.
Pliskova, 22, took advantage of a slew of miscues from the eighth-seeded Serb during an 80-minute match in Louis Armstrong Stadium to clinch her most successful grand slam appearance.
Ivanovic, 26, double-faulted seven times and committed 29 unforced errors as she had trouble handling the heavy, flat groundstrokes from the Czech.
"It's definitely my best match this year," said Pliskova, who has yet to win on the WTA Tour but who has twice been a runner-up this year.
"I didn't have that much strategy. I just went and played my game. I want to enjoy myself and I did it."
Pliskova will meet either 29th seed Casey Dellacqua of Australia or China's Wang Qiang in the third round. (Reporting by Larry Fine; Editing by Frank Pingue)