Doha, Qatar :Serena Williams became the first player to clinch a spot in the semifinals of the Sony Ericsson Championships after beating Elena Dementieva 6-2, 6-4 on Thursday for her third straight win in the group phase of the tournament.
Williams was broken to trail 2-1 in the first set but then won seven straight games to take control of the match, moving the Russian around the court with her powerful ground strokes.
She converted her third match point when Dementieva sent the ball into the net, then pumped her fist and yelled "Finally!"
Williams, who secured the year-end No. 1 ranking after Dinara Safina pulled out with a back injury, has failed to get out of the round-robin phase of the season-ending tournament the last two years.
"I'm happy to finally do well," she said.
The win also means Williams' sister Venus is still alive in the tournament. She needs to beat Svetlana Kuznetsova in Thursday's late match to still have a chance of reaching the knockout rounds.
Dementieva, who rallied from a set down to beat Venus Williams in their opening match, didn't find her stride until trailing 2-0 in the second set, as the encounter failed to live up to their epic three-set Wimbledon semifinal - billed by many as the best women's match of the year.
Dementieva won the longest game of the match after converting her fifth break point to make it 2-1, and the set went with serve until the last game.
Earlier, Wozniacki needed two medical time-outs to treat her cramping left thigh in the third set and collapsed to the court sobbing and clutching both legs after netting a forehand at 30-15 in the last game. But she got back up and clinched the win when Zvonareva, who had saved two match points in the second set, netted a forehand on the third.
"I have absolutely no idea how I pulled it through, but I'm very happy about it," Wozniacki said.
It was the U.S. Open finalist's second win in the tournament, putting her on the verge of the semifinals.
Wozniacki said her leg started cramping at 3-1 in the third set.
"From there, it just got worse and worse," she said. "I'm feeling better now. I got to cool down, getting some massage. ... I'm going to do everything tonight to recover to be ready for tomorrow."
Zvonareva replaced Safina as an alternate and had a dismal start, losing her first four service games. At 3-2 in the second set, she needed a five-minute medical time-out to treat a bleeding nose, and the match looked headed for a quick finish after she lost the next two games at love.
However, Wozniacki allowed her opponent back into the match as Zvonareva won the next three games and then saved two match points when serving at 6-5 - the first thanks to a Hawkeye challenge after a line judge ruled that her forehand had gone wide.
The lucrative Doha tournament is the last WTA Tour event of the season for the eight top-ranked women, with the top two players from each group advancing to the semifinals. The winner pockes p to$155milin epndngonhe rsutsinth gou pas, where each win is worth $100,000.