Serena Williams continued her unbeaten march towards the WTA Tour Championships title -- which will be the icing on the cake of a successful season -- with a 6-4, 6-4 win over world number one Victoria Azarenka in Istanbul.
The American superstar already has the Wimbledon and U.S. Open titles already under her belt and completed her fifth-straight win over Azarenka this year -- Williams had already qualified for the last-four with a win over Angelique Kerber in her previous match.
"Like I said yesterday, what I felt was really positive about my match is I know I can do better," Williams said. "I've been practicing really hard, and I actually expected to play a bit better and hopefully I can as the tournament goes on."
Azarenka needs just one more victory to ensure she ends the season as the world number one. Only Maria Sharapova is capable of catching up with the 23-year-old.
"I had too many opportunities that I didn't use," the Belarusian said. "I feel like I didn't keep my discipline. When I had the right play, I was in control most of the times, but I just couldn't do it consistently today.
"I'll be sad for a little bit after today's match, but I'll bounce back strong for tomorrow," she added. "It's win or go home. I'll give everything I have to win because I want to stay a couple more days here and fight.
"I'm glad I have another opportunity to keep the dream alive."
Azarenka will slug it out against Li Na in the final game of the Red Group, after the Chinese kept her hopes alive of qualifying for the semi-finals with a straight-set 6-4, 6-3 win over Kerber, who crashed out of the tournament after losing all three of her matches.
"I had my first match yesterday but felt much, much better today -- I was more focused and concentrated on the court," Li said. "Angelique is very good in defense. My coach, Carlos, was telling me before the match to use more topspin and open the court -- I knew I had to change the space to win today."
In the White Group, Sara Errani kept is still in with a chance of qualifying for the semis alive after posting a three-set 6-3, 2-6, 6-0 victory over Sam Stosur.
"I think we played a good match," Errani said. "She was playing amazing in the second, and I'm happy that I kept my focus and stayed aggressive on the third."
With Sharapova having already qualified from the group, Errani will take on Agnieszka Radwanska in the final group game with the winner guaranteed a place in the semi-finals. "I'm happy to be here and I'm happy with how I'm playing," Errani added. "I just want to keep going.
"Radwanska is a very strong player. We've played some times before and I know her well. I hope it will be a tough match."
