World's no.1 Serena Williams is scheduled to face former Wimbledon Champion Petra Kvitova in the opening match of the WTA Championships in Istambul, Turkey.

Williams, who is guaranteed to finish the year on top of the WTA rankings, is out to win another major tournament this year after racking up the French and US Open Championships.

With eight of the best women's singles player participating in the event, Williams won't have the luxury of facing an easy opposition in her first match. Instead, the multi Grand Slam champions will be facing Kvitova, who once ruled the year-ending WTA Championship in 2011.

"It's a tough group. I have to be ready. That's the thing about this tournament and why it's so tough, you have to be ready from the first match on," Williams told the Associated Press on Monday.

Kvitova, on the other hand, is bracing for tough match against the best women's singles tennis player in the world.

"Both of the groups are very tough and I don't think you can choose anyone who you think is weaker," Kvitova said. "This means that it's going to be a big fight every day, every match."

Kvitova and Williams are grouped with Petra Kvitová and Agnieszka Radwańska in Red Group.

Meanwhile, world's no.2 Victoria Azarenka believed the groupings are very much competitive as it could get, adding that everybody has the ability to win this tournament.

"It's the best eight players in the world. Anybody who is here is going to be a challenge," said Azarenka, who is grouped with Li Na, Sara Errani, Jelena Jankovic in White Group.