Jessica Pegula easily defeated Coco Gauff, the US Open winner and her doubles partner, to book her spot in the season-ending WTA Finals in Mexico.

In an hour, Pegula defeated her fellow American in Cancun’s windy and rainy conditions, 6-2, 6-1.

Rain forced the postponement of the other semi-final between Aryna Sabalenka and Igi Swiatek till Sunday.

The game was canceled with Swiatek leading 2-1; the championship game was rescheduled for Monday.

If Swiatek of Poland defeats the Belarusian and wins the tournament, she might replace Sabalenka as the top-ranked woman in the women’s division.

If Sabalenka makes it to the final, she will undoubtedly maintain her top spot in the world rankings.

Fifth-ranked Pegula, 29, converted six of her ten break point opportunities and only once gave up the serve against Gauff, 19, who is ranked third in the women’s division.

“It’s probably my biggest final ever,” Pegula declared after winning. “It’s going to give me a lot of confidence going into next year.”

Play was stopped by rain twice in the second set, but Pegula prevailed against Gauff, who committed 25 unforced errors.

“I really well executed what I wanted to do,” Pegula remarked. “It seemed to function even better under the windy conditions.

“I was just trying not to get frustrated with my serve or returns or any funky kind of points that we had and just to keep my feet moving.”