Doha - Serena Williams was in tears on Friday after snatching an historic victory at the Qatar Open which ensured that she would become the oldest woman to hold the WTA Tour's world number one ranking.
The 31-year-old American's 3-6, 6-3, 7-5 victory over Petra Kvitova in the quarter-finals put her back on top of the world after an interval of two and a half years during which she sometimes thought she might never play again.
Williams had been 1-4 down in the final set of an outstanding match against the Czech, and her relieved smile, heavenward gesture and tears in her moment of triumph gave lie to her earlier statement that the number one position no longer mattered.
"I am so sensitive nowadays -- I am always crying, but I never thought I would be here again you know," said Williams in a reference to the pulmonary embolism from which she suffered in 2011, threatening her life as well as her career.
"I have been through so much and I never thought I would be here," she repeated.
The victory, which was due to her very special competitive spirit and instinct for finding a way when no clear direction is evident, earns her the top spot at an age six months older than her fellow American Chris Evert did at 30 years and 11 months.
That was more than 27 years ago, underlining Williams' status as one of the all-time greats, and possibly the finest woman player there has ever been.
"When I was down I heard people cheering for me and I don't get that all the time," said Williams, who will start her 124th career week at number one on Monday.
That's a total only bettered by Steffi Graf (377), Martina Navratilova (332), Evert (260), Martina Hingis (209) and Monica Seles (178).
But for a while on Friday an in-form Kvitova made her look vulnerable.
The Czech had come back from deficits in the second and third sets the previous day against Nadia Petrova, and now arrived brimming with confidence and wrong-footing, flat-hit ground strokes.
Williams, who has been suffering from a cold as well as a twisted ankle and a bad back, looked sluggish and uncertain.
Her outstanding serve was not itself, and a double fault in the sixth game cost her a break of serve which eventually led to the loss of the first set.
It was the first that Kvitova had ever won against Williams, but even after levelling at one set all the American still slipped into deep trouble.
She found it hard to read her opponent's inside-out drives, could not rediscover her serving rhythm and delivered another double fault on game point which led to a three-game deficit.
"Every time I looked she was hitting winners," Williams said afterwards. "But I thought, if I can just stay in here...."
Williams kept swinging the drives from side to side and changing the pace, but even after breaking back for 3-4 the danger was not over.
She had to serve to save the match at 4-5, before a spectacular drive volley, a successful Hawkeye replay challenge, and a brilliantly sharp backhand drive angle got her the decisive break.
She closed out the match to love, finishing with an ace.
"I am glad she is number one," said Kvitova with good grace. "She deserves it."
Williams now has a semi-final with Maria Sharapova, who has won the Qatar Open title twice and remains unbeaten in Doha after winning 6-2, 6-4 win against Sam Stosur, the former US Open champion from Australia.
It was Sharapova's 12th win in Doha, and afterwards she explained why she, outgoing world number one Victoria Azarenka and Williams had appeared so downbeat about the three-way struggle for the world number one ranking.
"It's pretty special," said the Russian. "But the ranking is always one of those things which depends on the other players' success and the tournaments that they play."
Azarenka moved closer to a second successful title defence in a row when she overwhelmed Sara Errani, the French Open finalist, 6-2, 6-2.
Last month she retained the Australian Open title.
The Belarusian's surprisingly emphatic win over the Italian means she has dropped a mere nine games in three matches.
Azarenka's semi-final will be a sequel to last year's contentious meeting with Agnieszka Radwanska.
The world number four from Poland came from 0-3 and 3-5 down in the second set to win 6-2, 7-5 against Caroline Wozniacki, the former world number one from Denmark.