US Open champion Coco Gauff double-faulted four times in a row while serving for the second set and wound up losing 6-0, 7-5 to three-time major title winner Iga Swiatek in round-robin action at the WTA Finals on a windy Wednesday night in Cancun, Mexico.

There were plenty of empty seats at the temporary hard court — and Swiatek noticed.

"It's a shame that we don't have a full stadium," she said afterward.

"Hopefully for the future, there's not going to be any more situations like this, and they're going to work to improve it," Swiatek said.

The WTA's decision to host the event in Cancun was not announced until September.

In another singles match on Wednesday at the season-ending championship between the top eight women in tennis, three-time major finalist Ons Jabeur defeated Wimbledon champion Marketa Vondrousova 6-4, 6-3.

The two women, who will advance to the semifinals from this group, will be determined on Friday, when Swiatek (who is 2-0 so far) faces Jabeur (1-1), and Gauff (1-1) meets Vondrousova (0-2).

On Wednesday, Gauff led 4-2 in the second set, then was a game away from forcing a third while serving at 5-4. The teenager from Florida went up 15-love, then dropped the game with the series of double-faults. After the fourth, Gauff spiked her racket, before tossing it at her bench as she walked to the sideline.

That was part of a stretch in which the American lost nine points in a row, and 12 of the last 13 against Swiatek, who improved to 9-1 against Gauff.

Earlier, Gauff had hurled her racket after an errant backhand return late in the lopsided opening set.

Agencies via Xinhua