Azarenka beats Williams to lift Qatar title
The Belarusian defied the pair's career head-to-head statistics, which read 11-1 to Williams prior to the match, by meeting, and topping, her opponent's power to win 7-6(6) 2-6 6-3 in two hours and 28 minutes.
After edging an evenly-matched first set, Azarenka was out-played in the second as her serve consistency dropped off leading to two breaks by Williams.
That forced a decider but, crucially, the 23-year-old had made Williams serve for the previous set and she was able to re-gather her nerve and start strongly.
She broke Williams at the first opportunity and with her own first serve percentage back up to 80% she held off Williams to take the set and the title.
Her win means she remains unbeaten in 2013 and may feel hard done by that the No. 1 status will pass to Williams on Monday morning, particularly as she also took the first grand slam of the year in Australia.
Williams' renewed residency as the official world No. 1 was confirmed when she reached the semi-finals in Qatar. At 31 she will become the oldest No. 1-ranked female player since the introduction of computer rankings in 1975.