Having failed to reach any great heights on the American hard-court swing, the Czech, seeded third, will have fancied a deep run in the final tournament before the last grand slam of the year, which begins in New York on Sunday.
But she was ousted in straight sets in New Haven as Zhang dropped only three games in a 6-2 6-1 whipping and must now head to Flushing Meadows with just four victories since winning in Birmingham on the grass back in June.
WTA New Haven
Radwanska through to last four of Connecticut Open
It was also a bad day for fourth seed Kristina Mladenovic and seventh seed Barbora Strycova as they both crashed out.
Frenchwomen Mladenovic went down 7-5 7-5 to Hungary's Timea Babos while Strycova was beaten 7-5 6-3 by Russian Daria Kasatkina.
There was a rare win for Eugenie Bouchard, who beat America Laura David 6-1 6-4 to register just a third victory since the Madrid Open in April, while Elena Vesnina's slump shows no sign of ending as she lost 7-5 7-5 to Ana Bogdan. Since winning in Indian Wells in March, the Russian has not got to the quarter-final of any event.
Anastasia Pavlyuchenkova beat Christina McHale 3-6 6-2 6-4, Kirsten Flipkens saw odd Lesia Tsurenko 6-2 6-3 while Daria Gavrilova edged a hard-fought contest with Kristyna Pliskova 7-4 4-6 7-5.
Results from the New Haven Open Women's Singles Round 1 matches on Monday
- Zhang Shuai (China) beat 3-Petra Kvitova (Czech Republic) 6-2 6-1
- Kirsten Flipkens (Belgium) beat Lesia Tsurenko (Ukraine) 6-2 6-3
- Eugenie Bouchard (Canada) beat Lauren Davis (U.S.) 6-1 6-3
- Daria Gavrilova (Australia) beat Kristyna Pliskova (Czech Republic) 7-5 4-6 7-5
- Timea Babos (Hungary) beat 4-Kristina Mladenovic (France) 7-5 7-5
- 8-Peng Shuai (China) beat Katerina Siniakova (Czech Republic) 1-6 6-3 7-6(3)
- Ana Bogdan (Romania) beat 5-Elena Vesnina (Russia) 7-5 7-5
- Magda Linette (Poland) beat Roberta Vinci (Italy) 6-3 6-1
- Elise Mertens (Belgium) beat Kiki Bertens (Netherlands) 4-6 6-4 6-2
- Daria Kasatkina (Russia) beat 7-Barbora Strycova (Czech Republic) 7-5 6-3
- 6-Anastasia Pavlyuchenkova (Russia) beat Christina McHale (U.S.) 3-6 6-2 6-4
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