Maria Sakkari won 6-2, 6-4 against Iga Swiatek on Thursday in the round-robin stage of the WTA Finals in Guadalajara.
No. 4 seed Sakkari and No. 5 seed Swiatek battled it out for 86 minutes, with Sakkari winning 26 of 27 first-serve points.
Her win takes her 8-4 against the top 10-ranked opponents this year at tour-level events.
Sakkari is enjoying a breakthrough year having reached the semifinals of the French Open and US Open to reach a career-high world ranking of number six.
She is the first Greek woman to qualify for the WTA Finals.
Sakkari and Swiatek will face off twice more in the round-robin event.
Source: WTA Tour