American wild card Alison Riske routed 2011 Wimbledon champion Petra Kvitova to extend her sensational summer and reach a Grand Slam round of 16 for the first time.
The 81st-ranked Riske won 6-3, 6-0 on Saturday, taking the last eight games against the seventh-seeded Czech. She was 0-5 at major tournaments before Wimbledon this year but is 5-1 since.
The 23-year-old Pittsburgh native just broke into the top 100 in late July; now she'll likely earn a top-60 ranking.
This was Riske's first victory over a top-10 opponent.
Kvitova called for a trainer before the final game. She has always struggled at Flushing Meadows, the only major tournament at which she hasn't made the semifinals. Kvitova had seven double-faults and 27 unforced errors.