SINGAPORE (AP) — Venus Williams returns to the year-end WTA Finals for the first time since 2009 and will face Karolina Pliskova on Sunday.

The top eight players in the world will play in the round-robin event, which also features No. 1 Simona Halep, Garbine Muguruza, Elina Svitolina, Caroline Wozniacki, Jelena Ostapenko and Caroline Garcia.

"They're all pretty special," said Williams of her five career appearances in the year-end competition. "Only top eight get here. It's definitely something well-earned."

The 37-year-old Williams is the third-oldest player to qualify for the finals. Billie Jean King was 39 in 1983 and Martina Navratilova was 38 in 1994.

The fifth-ranked Williams reached two Grand Slam finals this season. She lost to her sister Serena at the Australian Open and to Muguruza in the final at Wimbledon.

Williams won the 2008 WTA Finals by defeating Vera Zvonareva of Russia. Since her first full season on the WTA Tour in 1995, Williams says she's seen improvement in the sport.

"The competition is so much greater," said the seven-time Grand Slam winner in singles. "It's a beautiful change, in fact."

Every player but Garcia has a possibility of reaching the year-end No. 1 ranking, depending on their result this week.

Williams is in the White Group, joining big-hitters Muguruza and Pliskova, who were both ranked No. 1 during this season. French Open champion Jelena Ostapenko is also in that group.

Williams and Pliskova are 1-1 in career meetings. Williams is 3-2 against Muguruza and 1-0 against Ostapenko.

"I think my group is more aggressive-style players," Pliskova said. "The other one is more defending.

"I start with Venus tomorrow. I beat her once from match point and once I lost a very close match. This one is open."