Anastasia Pavlyuchenkova inflicted yet another defeat on Angelique Kerber on day one of the WTA Elite Trophy after CoCo Vandeweghe and Julia Goerges made winning starts in Zhuhai.
Kerber spoke of her desire to finish a miserable year on a high note in China, but fourth seed Pavlyuchenkova beat the former world number one 6-3 3-6 6-2 in the Rose Group on Tuesday.
After the highs of winning her first two grand-slam titles in 2016, the 29-year-old has plummeted from the top of the rankings as recently as March to 19th coming into the tournament.
This was her third loss of the year to the Russian world number 14, each meeting having come down to a final set.
Eighth-seed Kerber has won only one of her last six matches and made a disappointing start to her final attempt to win a first title in 2017, Pavlyuchenkova making only 20 unforced errors to the German's 26 and breaking five times to seal victory.
Vandeweghe came out on top in the first match of the event, coming from a set down to defeat wildcard Peng Shuai 3-6 6-3 6-2 in the Bougainvillea Group.
Second-seed Vandeweghe had managed only a solitary victory in her previous four events in China and that record looked unlikely to improve when she was broken twice to lose the first set.
But the US Open and Australian Open semi-finalist raised her game from there and Peng was unable to pull off a victory in her homeland.
Goerges, meanwhile, is the early leader of the Azalea Group as a result of her 6-1 7-6 (7-5) success over Magdalena Rybarikova.