Serbia’s Ana Ivanovic just missed out on a place in the semi-finals of the season-ending WTA Finals despite beating Simona Halep in the final group match yesterday.

Under the rules of the round-robin competition, Ivanovic needed to win in straight sets to leapfrog Serena Williams in the group standings and snatch the last available semi-final spot.

But after coming from 5-2 behind to win the first set in dramatic fashion, she was unable to finish off Halep in the second, and had to settle for a 7-6 3-6 6-3 consolation win.

The result was a bittersweet outcome for Ivanovic. Although she won two of her three group matches and handed Halep her only defeat, she missed out on the semis because she lost one more set in her three matches than both the Romanian and Williams.

Halep, runner-up at this year’s French Open, faces Agnieska Radwanska in today’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 US Open final.

Earlier, Williams clinched the year-end world no.1 ranking for the fourth time without hitting a ball after Maria Sharapova, the only woman with any chance of overtaking her, was eliminated from the tournament.

Needing a straight sets win to stand any chance of advancing to the semi-finals, Sharapova lost the second set of her match against Agnieszka Radwanska, ending her hopes of overhauling Williams for the top spot.

Sharapova had led 7-5 5-1 but Radwanska dug deep to force a tiebreak, which she won 7-4.

Sharapova had already lost to Wozniacki and Petra Kvitova in the White Group and although she went on to beat Radwanska 7-5 6-7 6-2, the win served only as a consolation.