Vondrousova, making her debut at the WTA Finals, took an early 2-0 lead in the opening set after breaking Swiatek in the first game.

Swiatek, though, soon wiped out that advantage after forcing home a break chance of her own to level at 2-2.

In humid conditions, both players were feeling the pressure on serve as another untidy background return from the baseline by the Pole allowed Vondrousova to immediately break again.

The Wimbledon champion maintained the pressure to break Swiatek in the seventh game, the Pole this time sending a return into the net.

Following the change of ends, Swiatek made the most of the new balls to prevent Vondrousova serving out the set and then produced a solid hold to reduce the deficit at 5-4.

Vondrousova's early momentum had gone as Swiatek stepped up her offensive play to claim another break and level the opening set.

Swiatek, who can end the year by regaining the world number one spot, took the first set on a tie break and waltzed through the second in just over half an hour.

Monday's other match saw US Open champion Coco Gauff need less than an hour to beat Ons Jabeur 6-0 6-1.

Gauff won the first seven games before an hour-long rain delay, Jabeur finally getting on the board after the restart before the American completed the win in 57 minutes

On Sunday, world number one Aryna Sabalenka opened the finals with a straightforward win over Maria Sakkari.

Sabalenka later took to social media to criticise the arrangements for players at the season-ending championships, with Cancun only announced as the host venue less than two months ago.

Swiatek added her criticism to the court - laid on top of a golf course - saying "it's not comfortable" while Vondrousova described it as "very bad".

Sabalenka faces Jessica Pegula, who also won her opening group match, on Tuesday night with Sakkari facing Elena Rybakina.

READ MORE: Andy Murray loses his cool after Alex de Minaur's epic fightback at Paris Masters

RISHI-SUNAK

Prime Minister praises'swift hands' of Jonny Bairstow in halting Lord's protest

Editors Pick