Istanbul - Serena Williams beat Maria Sharapova 6-4, 6-3 Sunday to win the WTA Championships for the third time and finish the year with another title, but not the top ranking.

Williams ended the year with a 59-4 record. Since her first-round loss at the French Open, she is 31-1, winning Wimbledon, the Olympic gold medal and the U.S. Open.

The 31-year-old Williams became the oldest player to capture the year-end championships. She won seven titles this year.

"Now that I can be honest, I really wanted to win," Williams said. "I wanted it so bad but I didn't want to say it. ... It was really important for me to end the year with this title in particular."

But she will finish the year ranked No. 3, behind No. 1 Victoria Azarenka and No. 2 Sharapova, because she did not play as well in the first half of the year. Azarenka lost to Sharapova in the semifinals.

"I had such a good year, it was important to end on a good note," Williams said. "It was good for my sanity to win. I really wanted it although I didn't need it."

In 2001 and "09 Williams also won the elite, year-end tournament that brings together the top eight players.

A fist-pumping Williams closed the first set with an ace, one of 11 she had in the match. The American broke serve to start the second and was never threatened again. Williams hit a powerful return on her first match point. She finished with 40 winners to Sharapova's 13.

"Today she had another great serving day against me," said Sharapova, who never had a break point.

Williams finished the tournament without dropping a set. She also beat Azarenka in round-robin play, one of her four wins against the No. 1 this year.

"If I'm playing well and doing everything right, it's pretty difficult to beat me, without trying to sound too full of myself," Williams said. "And I hate to lose."

She has won 12 straight against opponents ranked No. 1 or No. 2 and has not lost to a player ranked in the top 2 since 2007.

Del Potro wins Swiss title

Juan Martin del Potro took Roger Federer's Swiss Indoors title at Basel, Switzerland, beating the hometown favorite 6-4, 6-7 (5), 7-6 (3) in the final.

Del Potro showed an impressive all-around game to help avenge a heartbreaking loss to Federer in the Olympic semifinals at Wimbledon in August.

"It was an unbelievable final," said Del Potro, who never dropped serve and raised his game in the decisive tiebreaker. "You can't wait, you have to go to (get) the victory."

Federer, who won the event in five of the past six years, was seeking his 77th career title to tie John McEnroe at fourth on the Open Era list.

"I didn't play a good tiebreaker in the third and that was the story of the match," said Federer, offering generous praise to his opponent who won the 2009 U.S. Open then sustained a serious wrist injury. "I definitely think he is right there again."

Federer later pulled out of his defense of the Paris Masters, which starts Monday, to rest and prepare for the ATP World Tour Finals in London the following week.

Ferrer takes Valencia title

David Ferrer won the Valencia Open in Spain for the third time, beating Alexandr Dolgopolov 6-1, 3-6, 6-4.

Ferrer also won on the hard courts in 2008 and 2010.