Two more semifinal spots and year-end No.1 are up for grabs today - here's what you need to know.
WTA Staff

ISTANBUL, Turkey - When the Top 8 players assemble in one city, not only are there going to be thrills on the court, but some great nuggets for all of the stats fans out there. This week will bring you stats to chew on, from that day's matches to scenarios to some other Turkish delights...

It's the fourth and last day of the round robin part of the TEB BNP Paribas WTA Championships - Istanbul 2012, and there are two big things on the line today - the two remaining semifinal spots and the year-end World No.1 ranking.

Usually in a round robin format, qualifying for the semifinals can depend on everything from matches won to matches played, head-to-head, sets won, even games won if it really gets down to it. But today it couldn't be simpler:

The semifinals will be...
Williams vs [winner of Radwanska vs Errani]
Sharapova vs [winner of Azarenka vs Li]

While we know Williams will finish the year at No.3 and Radwanska will finish the year at No.4, the Top 2 is as of yet undecided. But like the semifinal scenarios, the scenario for the year-end No.1 ranking couldn't be simpler:

For Sharapova to be year-end No.1...
- Sharapova must win today, win her semifinal and win the final
- Azarenka must lose today
Anything else and Azarenka will be year-end No.1...

Friday: Round Robin, Day 4.

(2) Maria Sharapova (RUS #2) vs. (Alt) Samantha Stosur (AUS #9)
~ Head-To-Head: Sharapova leads Stosur, 10-2
~ It looks like Sharapova dominates the series, but there has been a major shift in power over the last year: while Sharapova started the head-to-head off 9-0, seven of those wins coming in straight sets and the other two with routine third sets, Stosur has gone 2-1 against her over the last 12 months, holding match point in the only loss and the two wins coming in straight sets

~ This match has no effect on the semifinals, with Sharapova guaranteed to finish No.1 in the White Group and Stosur unable to move through
~ Sharapova does need to win this to keep her hopes of year-end No.1 alive
~ Stosur has won seven of her last 11 matches against Top 2 players

(4) Agnieszka Radwanska (POL #4) vs. (7) Sara Errani (ITA #7)
~ Head-To-Head: Radwanska leads Errani, 5-1
~ Their first four meetings might not be very telling, as they were in ITF Women's Circuit events and WTA qualifying (Radwanska up 3-1 in those); they have played twice in WTA main draws and Radwanska has won them both handily, at Wimbledon in 2010 (63 61) and Madrid earlier this year (60 61)

~ The winner of this match will advance to the semifinals (vs Williams)
~ Errani was 0-28 against Top 10 players going into the French Open but is 5-4 since then (two wins over Stosur, two wins over Kerber and one win over Bartoli); however, she is a dubious 0-22 against Top 5 players going into this one

(1) Victoria Azarenka (BLR #1) vs. (8) Li Na (CHN #8)
~ Head-To-Head: Series Tied, 4-4
~ The series is even, but Azarenka has won their last three meetings - then again, both of their 2012 meetings have gone to three sets (Azarenka winning 62 16 63 in the Sydney final and 36 63 63 in the Madrid quarterfinals)

~ The winner of this match will advance to the semifinals (vs Sharapova)
~ If Sharapova lost to Stosur, Azarenka will be year-end No.1
~ If Sharapova beat Stosur, Azarenka can clinch year-end No.1 by winning this (and even if she loses this she'll get it if Sharapova doesn't win the title)
~ Li has two wins over World No.1s: Williams at 2008 Stuttgart and Wozniacki at 2011 Australian Open (she is trying to become the first Chinese to have three wins over World No.1s - Zheng also has two wins over World No.1s)

BONUS STAT: Radwanska & The Number 7
Agnieszka Radwanska has had a pretty good friendship with the number seven - she has never been ranked No.7, but she has played World No.7s seven times before (it would be spooky if she were 7-0 against them, but she's 6-1):

Radwanska Vs No.7s
d. No.7 Dementieva, 63 62 (2008 Istanbul F)
d. No.7 Kuznetsova, 62 75 (2008 WTA Championships RR)
d. No.7 Ivanovic, 61 36 64 (2009 Rome 3r)
l. No.7 Kuznetsova, 64 16 61 (2009 French Open 4r... went on to win title)
d. No.7 Dementieva, 64 63 (2010 Miami QFs)
d. No.7 Schiavone, 63 62 (2011 Eastbourne 2r)
d. No.7 Bartoli, 64 62 (2012 Miami SFs)

... Radwanska has never been ranked No.7 herself - after spending years hovering at No.10, No.9 and No.8, she skipped to No.6 after the Australian Open earlier this year and then climbed to No.5, No.4, No.3 and No.2.

Watch live action from Istanbul on WTA Live powered by TennisTV!