Good afternoon everyone. The WTA Championships semi-finals are here and Sports Mole will be bringing you coverage of both matches today. First up, it's Li Na vs. Petra Kvitova.

Plenty of people will be backing Serena Williams to win this tournament again but in this sport, you just never know when a shock is coming. Williams and Jelena Jankovic take centre stage later on this afternoon.

Li finished top of the White Group to book here spot in the semi-finals but she will face a tough challenge against Kvitova, who won this tournament in 2011.

Kvitova and Li have previously met on six occasions, with each player claiming three wins. That statistic shows you just how evenly matched these two competitors are. We could be in for a very tight contest this afternoon.

Both players have been introduced to the crowd and the action is just a few more minutes away. I think the first set will be crucial in this match. Both players rely a lot on confidence and a great start would make a difference.

It might not be the semi-final that people were expecting but both players can produce some magic when they bring their best to the court. The warm-ups are over and it will be Kvitova who serves first.

BREAK! A big first serve earns Kvitova here first point before Li strikes back with a brilliant cross-court backhand. The Czech then hits a forehand too far to offer the advantage to her rival. Brilliant from Li as she secures two break points by sending Kvitova the wrong way with a great forehand. Kvitova strikes a forehand straight into the net and Li has break of serve in the first game!

Kvitova fires the ball into the net in the first point of the game. A long rally is ended by a beautiful volley by Na, who is using the court superbly early on. An unforced error hands Kvitova the next point and the 2011 champion levels the scores with a great forehand that just clips the line. The Czech takes on a second serve but she pushes too hard with the forehand. Deuce comes when Li serves a double fault but an unforced error from Kvitova hands the Chinese number one advantage. Li then secures a difficult hold of serve with a backhand past the on rushing Kvitova.

BREAK! Poor start to her second service game from Kvitova, who gifts Li the lead with a couple of disappointing unforced errors. Li spots an opening when Kvitova gets her length wrong but she fires a forehand into the net. Two big serves earn the Czech a 40-30 lead but it's deuce again following a long backhand. Li has the chance to break serve again when Kvitova double faults but two excellent serves secures advantage for the Czech. Kvitova fails to close out the game and another double fault earns Li advantage. However, Kvitova fights back again to once again come close to winning the game until some excellent defensive work from Li makes it deuce for the sixth time. There's groans from the Czech when she double faults for the third time in the game. Li then secures a second break of serve after seven deuces and 10 minutes when Kvitova fires a forehand into the net.

BREAK! Kvitova looks the be finding some rhythm during a long rally at the start of a new game but a poor forehand hands her rival the first point. The Czech pulls a point back but Li then displays great technique to fire a high volley down the the line. Kvitova looks to be out of the next point but a brilliant cross-court backhand delights the crowd and she builds on that by earning a break point. Li mishits a forehand and hands a break back to Kvitova. That could be crucial.

Kvitova struggles to build any momentum as she gifts Li a 0-30 lead with a couple of unforced errors. Two good serves make it 30-30 before Li's attempt to find the line with a forehand ends with the ball drifting out. Another confident serve helps Kvitova to hold her serve for the first time in the match.

An unforced error from Kvitova and the first two aces of the match see Li cruise into a 40-0 lead in a matter of seconds. However, a double fault follows to open the door slightly to Kvitova, who then pulls another point back when Li fires a shot into the net. Another big serve from the Chinese player helps her secure the hold.

Much better from Kvitova as she safely holds her own serve. The Czech player serves well throughout the early stages of the game to move into the lead. However, Li fights back with a brilliant backhand down the line. Kvitova stays strong though and a great drop volley wins the game.

BREAK! Kvitova attacks the second serve but her forehand goes long. Li once again uses the court well to manipulate her opponent, who then drills a backhand into the net. A big serve followed by an in-to-out forehand earns Li a 40-0 lead. Kvitova fights back in the middle of the game to make it deuce thanks to a couple of unforced errors and a superb volley. The Czech then displays some of her best tennis yet as some huge ground strokes provide the opportunity to break serve. Despite a fightback from Li, Kvitova finds another break point. Li clips the line to produce an ace at a crucial stage. The Chinese number one challenges unsuccessfully when a forehand goes long and Kvitova breaks back again thanks to another unforced error. The scores are level.

BREAK! Great tennis from Kvitova as she follows a wider backhand with a brilliant forehand to take the lead in the game. However, a couple of mistakes during the next two points gifts Li a 15-30 advantage. Two good serves bring Kvitova the next couple of points but some sloppy tennis then hands a break point to Li. Kvitova then strikes back to claim the advantage but a double fault at a crucial moment hands Li another great opportunity. Excellent movement from Li on break point and a powerful cross-court backhand gives her the lead again. She will now serve for the first set.

SET! Li starts the game confidently to win the first point but an unforced error into the net levels the score. A nervy shot from Kvitova goes long but it's 30-30 when Li's cross-court forehand lands a couple of inches wide. Li is far too short in the middle of a rally and that allows Kvitova to drill a forehand to claim a break point. The Czech player loses some of her rhythm towards the end of the game, which gifts Li set point. No mistakes from Li as a massive serve secures the first set.

Li deserves the lead at this stage. It's been difficult at times but a lack of consistency from Kvitova means the Chinese number one has been able to secure victory in the crucial first set. Kvitova will get the second set underway.

BREAK! Li starts the second set with a beautifully placed forehand to claim the lead before an unforced error from Kvitova doubles the leader's advantage. Kvitova fights back to 15-30 but another wild shot gifts Li a break point and she makes no mistake at the start of the second set as she drills a forehand past the Czech to claim a break of serve. Big moment.

Li fails to immediately build on her advantage as Kvitova races into a 0-40 lead due to some loose hitting and inconsistent serving. Kvitova fights to stay in the next point but her cross-court backhand on the run just misses the baseline. Li then pulls another point back but Kvitova breaks back when a backhand goes long from the Chinese player.

Kvitova plays her best tennis of the match to quickly hold her serve after breaking. Two big ground strokes secure the lead early in the game but the best moment comes when the Czech approaches the net to play a delicate drop volley. Li fires a return of serve in the net to hand the game to her opponent.

There's signs that Kvitova's confidence is growing as she comes to the net again but a mistake when playing the second volley sees the ball crash into the net. Li's movement is something to be admired and her ability to keep two rallies going in the middle of the game earns her a 40-0 lead. Brilliant! Li approaches the net confidently but Kvitova executes the perfect lob shot to pull a point back. However, an unforced error follows and Li holds her serve.

BREAK! Classy from Li, who opens her body to drill a brilliant return winner down the line. Kvitova replies with a superb cross-court backhand for a winner of her own. Li leads again thanks to a forehand into the net from Kvitova, who responds by clipping the line with a powerful volley. It's break point Li following another superb winner, this time off the forehand and the serve is broken when Kvitova's shot on the run goes long. Li moves a step closer to the final.

Li's consistency and battling qualities might well win her this match. Some solid ground strokes early in the game brings a couple of unforced errors from Kvitova, who manages to stay in the game when Li drills a forehand wide. The Czech player has the opportunity to hit back immediately when another mistake offers her a break point. Kvitova fails to play the next point patiently and a nervy backhand sails wide. However, Li stays strong on her serve and it's an ace that allows her to hold.

BREAK! Li attacks the second serve but her backhand finds the net. Kvitova pushes her opponent wider but fails to find the line with her forehand and a looks of despair tells the full story. Li once again misses with her return to fall behind but some brutal ground strokes force Kvitova into a desperate, and unsuccessful, lob shot. Kvitova moves ahead 40-30 but her sixth double fault of the match opens the door again for Li, who then receives a break point when the Czech goes long with a forehand. Li attacks the serve with confidence to take control of the point and another unforced error means the Chinese number one will now serve for the match.

GAME, SET, MATCH! Li starts the game with a disappointing double fault but an impressive second serve secures her the next point when Kvitova drills a backhand into the net. The 31-year-old then clips the line with an ace as her confidence on serve continues to improve. An approach to the net ends with a convincing forehand to bring up two match points. The first one is wasted when Li delivers her second double fault of the game. Kvitova then fires a wild forehand wide and Li books her place in the final!

Excellent from Li, who becomes the first player to secure her place in the final. Kvitova just didn't bring her best today and she only showed flashes of what she can do on the court. Li battled superbly and she fully deserved the victory.

That victory also ensures that Li will become the new world number three. She will meet either Jelena Jankovic or Serena Williams in tomorrow's final. You can watch that second semi-final on Sports Mole today.