Catch up on all the WTA news from Istanbul and beyond, including impressive wins for Aga and Serena and Maria's quest for No.1.
WTA Staff

Every week there's a lot happening on the WTA - on the court, off the court, by the numbers, even a few tweets... catch up on it all in this week's WTA Diary.

The Magic Number
For everyone's favorite East Coast hip hop trio, De La Soul, three was the magic number.

However, for the WTA's resident sorceress Agnieszka Radwanska, it's four; on Tuesday, at the fourth time of asking she finally got the better of Petra Kvitova, producing two sets of beguiling tennis to triumph in their WTA Championships opener.

Off To A Flyer
Also making winning starts in Istanbul were Maria Sharapova and Serena Williams, who both impressed in straight set victories over tournament debutantes Sara Errani and Angelique Kerber.

And don't worry if you missed any of the action, you can catch up on all the best bits with the WTA's All Access Pass.

Top Dog
Maria's win keeps her dream of snatching the year-end No.1 ranking from arch rival Victoria Azarenka's grasp alive. To do so she needs to win the title and hope for a slip up or two from the Belarusian along the way.

Here's what she said about the subject when quizzed about it in the build up to the tournament:

"I think it also has to do with how some of the other players do - I don't like to think about what I can't control in my destiny, what's not in my hands. It would be a great achievement, no doubt, but the more matches I win here the better chance I have of accomplishing it, so that's my biggest priority this week."

Who was the last German to beat a World No.1 and where did she do it?

Early Casualty
Unfortunately, less than 24 hours into the tournament, Istanbul has already suffered its first casualty, after Kvitova withdrew with a viral illness on Wednesday morning. The Czech is flying back to her home city of Prostejov to have some further tests and hopes to be fit in time for next week's Fed Cup final.

"Yesterday when I played I was shaking a lot and I thought that I was just suffering from nerves," Kvitova said. "But normally nerves are gone after first set, and it was actually during the whole match, so I thought that it's something wrong. That's why I have to pull out.

"I don't like to give up, so I'm feeling really disappointed. I'll try my best to be ready for the Fed Cup. I really want to play in front of our crowd, my family and friends and to win the title again."

Replacing Kvitova in the White Group will be Samantha Stosur.

Away From Istanbul
Talking of Stosur, last week in Moscow, the Australian came close to ending her 14-month title drought, losing an entertaining final to Caroline Wozniacki, 62 46 75.

One player who did manage to break her trophy duck last week was Venus Williams, who triumphed over Monica Niculescu in the Luxembourg final. It was the 44th title of her career - sister, Serena, is the only active player to have won more - and the first since winning in Acapulco in February 2010.

On The Up
The only player to push Venus in the Low Countries was former World No.9 Andrea Petkovic in a tight three set semifinal. After an injury-ravaged year, it's good to have Petko (and her moves) back on court.

I wanted to thank you guys for all your support, especially through the rough times. It means so much to me. Venus played more aggressive in the end and deserved to win. It was (most of the time) a pleasure to be part of this match. Thank you, guys. <3