• WTA Championships

Serena and Azarenka both tested in Istanbul

Serena Williams made it two wins from two at the WTA Championships on Wednesday, but she was hardly in impressive form against China's Li Na.

Williams, who beat Angelique Kerber on Tuesday, is sitting in a strong position in the Red Group after a 7-6(2) 6-3 triumph over Li, but victory did not come without exposing holes in the American's game. Twice she had the chance to serve for the first set in Istanbul, and twice she was broken to love in a sulky performance.

The pair exchanged three breaks in the first four games to set the tone for the match, with neither serve looking dominant. The Chinese player came out on top for a 3-1 lead, although she was then pegged back to 4-4.

Williams, utilising her power, broke again for 5-4, but then lost her serve to love as Li restored parity. The American was experiencing déjà vu moments later as - at 6-5 this time - she was broken to love again, but she raced through the breaker to take control of the match.

That control grew when she penetrated Li's first service game of the second set, but once again Williams instantly relinquished her advantage. Six double-faults in the match did not help, but Li's serve was equally brittle and a further break saw Williams move out to 3-1.

At that stage Williams' serve began to find its range and, having served a solitary ace up to that point, she fired off five more as she closed out victory in an hour and 50 minutes.

"I started out really strong in the first game but then I started making errors and Li has been playing great to qualify for this event. She started playing her game and playing really well," Williams said.

Victoria Azarenka need over three hours to beat Angelique Kerber © PA Photos

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World No. 1 Victoria Azarenka was second on court on Wednesday as she kicked off her campaign with a thrilling 6-7(11) 7-6(2) 6-4 victory over Angelique Kerber. Azarenka is in the same group as Williams and the pair will be expected to emerge as the two semi-finalists from the Red Group, although she very nearly lost her opener.

Australian Open winner Azarenka did not have things all her own way against Kerber, falling a break behind in game three of the first set as the German attacked her serve. Azarenka levelled at 3-3 when Kerber fired a forehand long, but then lost a high quality tiebreaker after 63 minutes of play - having led the breaker 6-2.

The world's leading player responded in typical fashion, breaking immediately in set two, but Kerber hit back to love for 4-4. Azarenka then totally lost her cool as she fell 0-30 down when serving to stay in the match - smashing her racket into the surface - but she forced another breaker that she this time won to restore parity.

The momentum was now with the favourite and she broke at the first time of asking again to lead the final set 2-0, only to instantly cede her advantage. Azarenka went ahead again to create the chance to serve for the match, but she simply could not shake off Kerber whose forehand was firing missiles from the back of the court.

Another breaker looked on the cards, but with Kerber serving at 4-5 Azarenka broke for victory, roaring at the crowd in delight after three hours on court.

In the final match of the evening, the top-of-the-table battle between Maria Sharapova and Agnieszka Radwanska in the White Group went the way of the Russian. Both women had won their opening matches, but Sharapova now sits top of the group after a 5-7 7-5 7-5 victory.

Radwanska denied Sharapova a single break chance in the opening set, penetrating her rival's delivery on one occasion to move ahead. It was a different story in the second as Sharapova created 10 break points, converting four to pull level.

The third proved another tight set but Sharapova outlasted her opponent. She claimed a crucial break of serve in the 11th game of the set before serving out the match with a booming ace wide on the deuce side.

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