American Venus Williams clinched a spot in the semifinals of the WTA Finals on Thursday by recording a 7-5, 6-4 victory over Garbine Muguruza in group play in Singapore.
Williams is the runner-up of the White Group. The winner of the group is Karolina Pliskova, who was beaten 6-3, 6-1 by Jelena Ostapenko on Thursday.
The fifth-seeded Williams overcame 26 unforced errors while disposing of Muguruza, the Spaniard who defeated Williams in this year's Wimbledon final. The match took one hour, 41 minutes.
"A win is a win, whether it's like today or yesterday," Williams said in her post-match press conference. "I'm pretty used to going home after you lose, so I knew what the stakes were."
The second-seeded Muguruza was hampered by 34 unforced errors, including a couple critical ones on volleys late in the opening set.
Muguruza jumped out to a 3-1 lead in the second set before Williams turned it on and won five of the final six games to finish the match.
"I think she played very good in important moments, and I made few mistakes that I shouldn't," Muguruza said afterwards. "I was just trying to not get crazy and kind of wait for my opportunity. And it didn't come. In important moments, she stepped up and turned it around."
Meanwhile, the seventh-seeded Ostapenko recorded her first win in three matches this week with a dominating performance against the third-seeded Pliskova.
The Latvian had 25 winners against just 14 unforced errors while finishing off the Czech in just 66 minutes.
"It was my last match here today," Ostapenko said during her post-match press conference. "I really tried to enjoy every moment. I think I was playing quite relaxed, and I just showed my best today.
"You have to be really prepared for every match, because players who get here, they play on a very high level, and every match will be a battle."
The French Open champ forced Pliskova into 17 unforced errors compared to just eight winners. Pliskova also committed five double faults.
Pliskova admitted her motivation wasn't high after previously clinching a spot in the semifinals.
"Really tough to push myself into it and to play the best tennis if you know you're qualified," Pliskova said. "Wasn't being ever in this situation, so I felt weird today."
Also, Martina Hingis and partner Chan Yung-Jan of Taiwan advanced to the doubles semifinals with a 6-3, 6-2 victory over Germany's Anna-Lena Groenefeld and the Czech Republic's Kveta Peschke. The win was the 19th in a row for the top-seeded duo and came on the same day the 37-year-old Hingis announced her retirement.
Hingis and Yung-Jan will face the third-seeded duo of Timea Babos of Hungary and Andrea Blavackova of the Czech Republic on Friday.