World number four Karolína Plíšková overcame a spirated Garbiñe Muguruza in a thrilling three-set encounter on the opening night of the WTA Finals in Guadalajara, Mexico.Plíšková is seeded third in the tournament, behind Aryna Sabalenka and compatriot Barbora Krejčíková and faced off against the former world number one for the 11th time in her career.The Czech star had dominated their head-to-head meetings in the past, but this was just the second time the 29-year-old had faced Muguruza since 2017.It was the Spaniard who took the first set 6-4 as Plíšková struggled to find her rhythm early on. But the Wimbledon finalist recovered well to take the second 6-2.With the match on a knife-edge, it was the Czech who held her nerve in the decider, finally securing victory in a tie-break after Muguruza saved three match points.ENTER GIVEAWAYENTER GIVEAWAYSpeaking afterwards, the third seed admitted she could afford to relax a bit more now that she had registered a win. Two victories will likely be enough to secure a spot in the semi-finals, meaning Plíšková could lose one of her next two games and still qualify."Honestly I think it's huge because, of course, you can relax a bit more,” she said. “It's not like you can lose the next match. Of course, nobody wants to lose any match. But it's like, okay, you have at least that one win, there's not such a pressure that you need to win every other match."If I just lose this match tonight, I think I'm gone because it was big, having couple match points, breakpoints there, I was so close to making it even before the tiebreak. Then, of course, I was quite close to also losing it."Meanwhile, Muguruza stressed she was satisfied with the way she played, despite suffering defeat. "I fought as hard as I could. In the end it was just one point difference. I'm actually proud of the match I played due to the circumstances. I loved the crowd. Even though I suffered during this match, I also felt very energized and motivated to play in Mexico."

Plíšková’s win put her joint top of the Teotihuacán group with Estonia’s Anett Kontaveit, who beat Krejčíková in straight sets.

The 25-year-old won back-to-back titles at the Kremlin Cup and the Transylvania Open to qualify for the Finals and is now on an 11-match winning streak.

Asked why her game has seemingly fallen into place, Kontaveit said: "I've been believing in myself a little bit more, and the game definitely has clicked from just getting more wins and playing a lot of tennis and really feeling comfortable and enjoying playing tennis."

Kontaveit faces Plíšková tomorrow, with the winner in pole position to make the final four in Guadalajara.