Serena clinches year-end world number one spot

* Serena clinched year-end top spot

* Safina forced out by back injury

(adds details, quotes)

By Martyn Herman

DOHA, Oct 28 (Reuters) - Serena Williams rarely backs down in a scrap but she was spared a fight for the honour of ending the year as world number one on Wednesday when her rival Dinara Safina quit the WTA Championships with injury.

The 28-year-old American was guaranteed finishing top for the first time since 2002 when Safina lasted just two games against Serbia’s Jelena Jankovic in her first match at the season-ending showpiece that had been billed as the duel in the desert.

Safina, who topped the standings for more than half the year but needed to at least match Serena’s performance in Doha to cling on to first place, made a tearful exit with a lower back injury before confirming that she would not attempt to play her other two round-robin matches.

Serena then went out and beat sister Venus in a family dust-up that ended past midnight, coming through 5-7 6-4 7-6 in a near three-hour contest that underlined the warrior instincts of the 11-times grand slam champion.

While victory virtually assured Serena of her place in the semi-finals, it left Venus’s hopes of retaining her title hanging by a thread after she suffered her second defeat in two days after falling to Elena Dementieva on the first day.

“2009 has been a truly memorable season for me during which I enjoyed some of my biggest career wins,” Australian Open and Wimbledon champion Serena told reporters.

“Capturing the year-end world number one ranking is a huge accomplishment for me and I am thrilled that all the hard work has paid off.”

She did, however, spare a thought for Safina despite often questioning the Russian’s credentials as a world number one this year on the basis that she has still to win a grand slam title.

“Dinara is such a great player that she must be really hurt because she never gives up,” Serena said. “It’s a shame for the tournament because it would have been great if we had both got through to the final to battle for it.”

While Serena’s tennis has been impressive this season, the small matter of an ITF disciplinary hearing is still hanging over her head after her foul-mouthed rant at a line judge during the semi-final at the U.S. Open which resulted in a penalty point against her on matchpoint down to Kim Clijsters.

Despite that unsavoury incident, WTA Tour chief executive Stacey Allaster congratulated Serena on her achievement.

“Serena is a terrific ambassador for our sport,” she said.

Williams, who will be number one through the week beginning Dec. 28 at least, is eighth in the list for total weeks spent as world number one since the WTA rankings came into force, having spent 83 weeks at the top.

(Reporting by Martyn Herman; Editing by Ed Osmond and Greg Stutchbury, to query or comment on this story email sportsfeedback@thomsonreuters.com)