Maria Sakkari was merciless as she began her WTA Finals campaign with a comfortable 6-2 6-4 win over an Iga Swiatek who became visibly emotional towards the end.

It was Sakkari's eighth win over a top-10 opponent this season, the most of any player on the WTA Tour, while the victory took her to 3-0 against Swiatek this year.

Sakkari, with her trademark intensity and feistiness, appeared to adjust to the conditions and altitude of Guadalajara much better than her opponent, who looked lethargic during the first set.

This was particularly evident in the 20-year-old's second service game, as Sakkari converted the second of her break points to get the early advantage.

Swiatek showed the occasional flash of quality, such as an awesome out-of-the-blue cross-court forehand in the fifth game, but she soon found herself 5-2 down as Sakkari broke to love, the decisive point gifted to her by a sloppy volley at the net that the Pole inexplicably put beyond the sideline.

Sakkari quickly wrapped up the set but Swiatek was able to dig a bit deeper in the second, showing great determination to eventually hold serve during the 10-minute third game.

But her body language at the change was hardly indicative of a player convinced she could level the match, as she sat there with a towel draped over her from head to knees.

Swiatek held out for another few games but Sakkari got the decisive break to go 4-3 up, and the match ultimately went with serve from there.

Sakkari finished her opponent off by serving to love, with a tearful Swiatek given a code violation for turning her back as she attempted to regain her composure before facing triple match point, ultimately putting her return into the net.

WINNERS/UNFORCED ERRORS

Sakkari – 15/22
Swiatek – 8/29

ACES/DOUBLE FAULTS

Sakkari – 2/5
Swiatek – 2/6

BREAK POINTS WON

Sakkari – 3/8
Swiatek – 0/2