The women's world No.1 ranking switched hands yesterday for the first time in almost a year but the identity of the next occupant of top spot still remains to be decided.

Caroline Wozniacki's 6-3, 7-6 defeat by Kim Clijsters, the defending champion, in the quarter-finals not only kept alive the Belgian's chances of winning a fifth grand slam title but also opened the door for any one of three women to take over at the top.

Going into last night's two remaining quarter-finals, Victoria Azarenka actually held the No.1 ranking, in theory, after reaching the semi-finals with a three-set win over Poland's Agnieszka Radwanska.

However, everything was dependent on last night's results of Wimbledon champion Petra Kvitova and the woman she beat in last year's final, Russia's Maria Sharapova.

In simple terms, Sharapova needs to reach the final to have a chance of being No.1, while if Kvitova matches or betters the efforts of Azarenka and Sharapova, then she would snatch top spot.

Martina Navratilova, who won 18 grand slam singles titles and 59 in total and who is here playing in the Legends doubles event, was brutally honest about the subject, saying: "Clearly, nobody feels Wozniacki is a true No.1."

It was harsh on the most consistent player on tour, who won six titles in 2011 but the Dane is convinced that she will bounce back.

"I've been there for a long time already and I finished No.1 two years in a row," she said. "In the end of the year we will see who played best. I'll get it back eventually, so I'm not worried."

What might worry her, however, is that another slam has gone by without her breaking her duck.

Though she fought back from 5-2 down in the second set to force a tie-break, she was second-best throughout against Clijsters, who hit with more power and intent, exposing the suspect Wozniacki forehand.

Clijsters leads Azarenka 4-2 in their head-to-head battles but with her movement to her left side restricted by a sore ankle, she knows the Belarussian will take some beating.

"It's going to be very important to be dominant," Clijsters said. "She's improved a lot on her fitness and her movement, which was definitely a weakness in the past. She's becoming a more and more complete player. I'll have to play some of my best tennis if I am to beat her."