Jessica Pegula beat Coco Gauff on Saturday to reach the WTA Finals title match but continuing weather woes saw Aryna Sabalenka's clash with Iga Swiatek suspended by rain.
World number one Sabalenka and number two Swiatek had played just three games when rain blew in, halting a match between players fighting for the year-end number one ranking.
If Australian Open champion Sabalenka wins, she'll finish the year atop the rankings, but if French Open champion Swiatek advances and goes on to claim the title she will regain the number one spot.
Whoever wins will have to get past a red-hot Pegula, who has not lost a set on the outdoor hardcourts in Cancun. Pegula shook off a late rain delay and windy conditions to dispatch US Open champion Gauff, her doubles partner, in an hour. "I executed what I wanted to do really well," Pegula said. "In the windy conditions, I think it worked even better. "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." There was no respite for Sabalenka and Swiatek from the weather that has wreaked havoc all week at the tournament.