World number one Justine Henin [Images] battled back from a set down to overcome Maria Sharapova [Images] 5-7 7-5 6-3 and retain her WTA Championships title in an epic struggle at the Madrid Arena on Sunday.

The 25-year-old Belgian had to draw on every ounce of her renowned reserves of grit and determination to shake off Sharapova in a thrilling match that lasted three hours 24 minutes, a record for a three-set final in the end-of-season tournament.

The victory extended Henin's winning streak to 25 matches and made her the first woman since Steffi Graf [Images] in 1989 to go unbeaten in the second half of the season, post-Wimbledon.

She also became the first player to claim 10 tour titles in a year since Martina Hingis [Images] won 12 in 1997, and the first to break the $5-million barrier in prize money in a season.

"In the third set it was much more mental and physical," said Henin who needed five match points to clinch victory.

"It was a tough last game, we were both dead. What a way to finish the season. I feel it's a dream what's happened this season."

Sharapova, who was back close to her best after struggling with injury problems for much of the season, said she was delighted with such a strong finish to the year.

"It's been a pretty rough year for me with all the injuries and two weeks ago I didn't even know if I was going to play here, let alone get to the final," said the 20-year-old. "I'm so thankful to have got here.

"I hope we can play many more times so I can get my revenge."

CONFIDENT START

Henin, who had won five of her previous seven meetings with Sharapova, made a confident start, winning her first service game to love and breaking the Russian's serve in the third.

Sharapova hit back immediately, earning two break points with a powerful forehand pass and slamming a deep return on to Henin's toes to take the game.

There was nothing to separate the two players until the 12th game, an epic affair in which Henin's serve let her down as she committed four double faults.

Henin managed to hang on and save seven set points before her serve finally cracked, a loose backhand giving Sharapova another chance to break and a miscued forehand allowing the Russian to take the set.

The match began to swing in Henin's favour when she broke in the ninth game of the second set with a wonderful, whipped cross-court winner.

Sharapova broke back when Henin was serving for the set but the Belgian won the next game to go 6-5 up and finally produced a solid service game to level the match.

Victory in the second set gave Henin a new lease of life and she finally found the sort of fluency that she had shown earlier in the season to break in the third game.

She saved three break points in the fourth before going 3-1 up and although Sharapova hit back in the next game the Belgian cracked her serve once again to lead 4-3.

Sharapova saved four match points in the final game before she eventually relented.

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