Caroline Wozniacki started her WTA Finals with a 6-2 6-0 thrashing of Elina Svitolina in Red Group.
Wozniacki, who qualified sixth for the season-ending event in Singapore, produced a sensational performance as she swept aside Svitolina in straight sets, recording her first win over the Ukrainian at the fourth time of asking.
The Dane has moved to the top of Red Group after the first round-robin matches, having dropped less games than the other players in the pool.
Speaking after her win, the 27-year-old said: "I played extremely well out there, I'm just really happy to be through this first match. I tried to stay aggressive and go for my shots - it really worked for me today."
In the earlier match on Monday, world number one and top seed Simona Halep managed to overcome in-form Caroline Garcia in straight sets, winning 6-4 6-2 to get her tournament off to a perfect start.
The Romanian was tested in the early stages by her French opponent but proved to have too much quality as she clinched victory in one hour and 28 minutes.
Halep also reacted to her opening win, saying: "I'm really pleased. It wasn't an easy first match against a player that beat me two weeks ago. I felt really well out there."
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