Top seed Daria Kasatkina has been knocked out of the WTA Elite Trophy, beaten 6-2 6-4 by Madison Keys.
Keys, 23, broke six times in a dominant display, leaving the Russian with one win and one defeat from her round-robin matches - and no chance of progress.
The American just needs to win a set on Friday against China's Wang Qiang - who requires a straight-set victory to go through in Zhuhai.
All four group winners at the 12-player event will reach the semi-finals.
The invitation-only event features the top 11 players who have not qualified for the top-tier WTA Finals, with space for one wildcard.