American Jessica Pegula powered into the semifinals of the season-ending WTA Finals in Cancun on Thursday, beating Maria Sakkari 6-3, 6-2 to complete an unbeaten run through the group stage.
Pegula, the oldest player in the field at 29, had already clinched her spot in Saturday's semifinals and Sakkari was already out of contention before the match on the Mexican outdoor hardcourts.
Pegula, who went winless last year in her WTA Finals debut, seized control early, leading 4-1 in the opening set on the way to a dominant victory in difficult, windy conditions.
She took full advantage of 35 unforced errors from Greece's Sakkari, including eight double faults, Pegula reaching the last four without dropping a set.
Pegula was pleased to keep things rolling in the unfavourable conditions, saying she tried to play to the middle of the court and keep down mistakes.
"It's so tough to play in these conditions," she told Tennis Channel. "You're trying to do your best and as soon as you get some momentum, you still feel like you could lose it.
"If you just stop moving your feet for one second, you get one unlucky shot. So you're very on edge.
"It was crazy out there today," she said.
Pegula's brisk run through her group matches included an upset of Aryna Sabalenka, the world No 1 who faced a do-or-die clash with fourth-ranked Elena Rybakina for the second semifinal berth from the group.
The two met in January in the Australian Open final, where Sabalenka triumphed in three sets for her first major title.
She had pushed her career record of Rybakina to 4-0 before the 24-year-old from Kazakhstan won two straight – in the Indian Wells final in March and in the quarterfinals at Beijing.
Sabalenka, who is one of several players who have complained about the condition of the court at this week's tournament, is not only gunning for the prestigious title.
She's also aiming to take the year-end No 1 ranking, which could still be claimed by Poland's reigning French Open champion Iga Swiatek.