Ana Ivanovic took three sets to beat Simona Halep, while she needed two to advance to the WTA Championship semi-fnals. So Halep advances out of the round-robin group,
Tennis-Ivanovic bows out despite beating Halep at WTA Finals
So where does that leave the tournament?
"Halep, runner-up at this year's French Open, faces Agnieska Radwanska in Saturday's semi-finals while Williams, who is chasing a hat-trick of WTA Finals titles, meets Caroline Wozniacki in a rematch of last month's U.S. Open final."
So Serena, despite being schooled by Halep, is still in the tournament, and will still be the favorite to win it.