An emotional Serena Williams has secured the No. 1 ranking after coming from a set down to beat former Wimbledon champion Petra Kvitova 3-6, 6-3, 7-5 to reach the Qatar Open semifinals Friday.
The 31-year-old American will become the oldest women's player to be No. 1 in next week's rankings.
Nursing a right ankle injury from the Australian Open, Williams struggled early on with the Czech's serve and forehand. But she went on to win 13 of the final 14 points in the second set.
Down 4-1 in the decider, Williams broke Kvitova when she double faulted to make it 4-3. Though it seemed the match would go to a tiebreaker, Williams broke with a wicked crosscourt backhand to make 6-5 and won it with one of her 14 aces.