Beijing - Simona Halep was beaten in the second round of the China Open on Monday by Russia's Ekaterina Alexandrova, with the Romanian appearing to struggle with a back injury.
The 28-year-old reigning Wimbledon champion lost 6-2, 6-3 in 64 minutes in Beijing to bring her tournament to an early end.
Halep, fifth in the world, was far from her best as she went down meekly to the 38th-ranked Alexandrova.
She was also forced out of last week's Wuhan Open because of her troublesome back.
Canadian teenager Bianca Andreescu had to dig deep as she won her first match since her US Open heroics.
The 19-year-old rising star defeated 60th-ranked Aliaksandra Sasnovich of Belarus 6-2, 2-6, 6-1 in what was at times an unconvincing performance, finishing the match with 31 unforced errors.
The world No six, who stunned Serena Williams in the final at Flushing Meadows, arrived in Beijing on a run of 13 wins in a row.
She looked all set to carry on her blistering form against Sasnovich and emphatically captured the first set.
But Andreescu struggled with her serve in the second, totting up six double faults and was in danger of losing her cool in the haze of the Chinese capital.
Normal order was restored in the deciding set, Andreescu breaking Sasnovich's first service game and then holding her own to take a 3-0 lead and an advantage she refused to surrender.
In round two the Canadian sensation plays Elise Mertens, the world No 23 from Belgium.
Results from the WTA/ATP China Open on Monday in Beijing (x denotes seeding):
Anastasia Pavlyuchenkova (RUS) bt Veronika Kudermetova (RUS) 6-0, 3-6, 7-6 (7/4)
Bianca Andreescu (CAN x5) bt Aliaksandra Sasnovich (BLR) 6-2, 2-6, 6-1
Elise Mertens (BEL) bt Petra Martic (CRO) 6-2, 6-3
Jennifer Brady (USA) bt Amanda Anisimova (USA) 6-7 (4/7), 7-6 (7/2), 6-3
Madison Keys (USA x11) bt Karolína Muchová (CZE) 6-4, 7-6 (7/5)
Caroline Wozniacki (DEN x16) bt Lauren Davis (USA) 6-1, 6-3
Kiki Bertens (NED x8) bt Dayana Yastremska (UKR) 7-6 (7/5), 6-3
Ekaterina Alexandrova (RUS) bt Simona Halep (ROU x6) 6-2, 6-3
Katerina Siniakova (CZE) bt Jelena Ostapenko (LAT) 6-2, 6-1
Zhang Zhizhen (CHN) bt Kyle Edmund (GBR) 6-4, 3-6, 7-6 (7/5)
Karen Khachanov (RUS x4) bt Pablo Cuevas (URU) 6-2, 7-6 (9/7)
Jeremy Chardy (FRA) bt Marco Cecchinato (ITA) 6-7 (7/9), 6-3, 7-6 (7/4)
Andrey Rublev (RUS) bt Grigor Dimitrov (BUL) 6-2, 7-5