Maria Sakkari won a rollercoaster match against Aryna Sabalenka 7-6 (7-1), 6-7 (6-8), 6-3 on Monday to advance to the semi-finals of the WTA Finals, where the in-form Greek will meet Estonian Anett Kontaveit.

Sakkari’s fitness proved the difference in the deciding set and she pumped her arms triumphantly when a worn down Sabalenka misfired on match point in the high-altitude Mexican city.

“It was a rollercoaster match from both of us,” said Sakkari, who had lost in her four previous meetings with the Belarusan.

The demonstrative top-seeded Sabalenka lost her temper at times during the marathon match, typically after issuing one of her 19 double faults.

Earlier in the day, Poland’s Iga Swiatek defeated birthday girl Paula Badosa 7-5, 6-4.

The stakes were low since the 24-year-old Badosa had already advanced to the semis, where she will meet fellow Spaniard Garbine Muguruza for the first time, and Swiatek had already been eliminated following losses to both Sakkari and Sabalenka.

“I’m pretty happy that I had a chance to show my tennis finally ... I really enjoyed myself today on court,” Swiatek said.