Serena Williams has the chance to reclaim the No 1 ranking at the Qatar Open, a spot the 15-time major champion has not held since October 2010.
The second-ranked Williams will become No 1 if she reaches the semi-finals of the tournament which features nine of the top 10 players.
If Williams falters, top-ranked Victoria Azarenka can guarantee herself the No 1 spot by reaching the final. Third-ranked Maria Sharapova also has a chance to return to the top if she wins the tournament, Williams fails to advance to the semi-finals and Azarenka doesn't reach the final.
Sharapova last held the No 1 ranking for four weeks in 2012 after the French Open.
Willliams is coming off an Australian Open in which she looked dominant at times but eventually lost in the quarterfinals to American teen Sloane Stephens. She also got injured along the way, hurting her right ankle in the first round against Edina Gallovits-Hall and then her back in the loss to Stephens.
The 31-year-old American said she was "feeling a little better" and that neither her back nor her ankle was bothering her at the moment.
"Just taking it one day at a time, basically," Williams said. "So I will see how I feel after my first match."
Williams lost the No 1 spot to Caroline Wozniacki in 2010 and then tumbled down the rankings due to injuries in 2010 and 2011. But she has played some of her best tennis in the past year, winning Wimbledon, the Olympic gold, the US Open and the season-ending WTA championships. She lost only one match in 2012 after her first round exit at the French Open and only once this year.
If she reached No 1 again, Williams would become the oldest player to hold that ranking.
"It will be great. I think it will be a great feeling," Williams said. "I obviously want it, but it's not the only thing I want, you know, so if it happens, great. If not, I won't miss anything, I don't think."
Azarenka said winning the tournament was all that mattered and the rankings would take care of themselves.
"It's the same story as I had two weeks ago I had at same press conference, the same questions. I'm just going to answer the same way: I'm here to win the tournament, and the ranking is a bonus that comes with it," Azarenka said. "There is no point to jump ahead. We still have to play the tournament. The ranking doesn't come out till the next Monday, so what's the point?"
But the 23-year-old Belarusian warmed to the idea of a three-way race for No 1, at least when it comes to raising the profile of women's tennis.
"I think it's exciting. Twitter and Facebook is blowing up so we have a lot of questions," Azarenka said. "But I think it's important also for the players to keep that competitive spirit, to kind of be on the watch out."
Sharapova, looking to return to No 1 for a fifth time, lost in the Australian Open semifinals to Li Na. But until then, the Russian had conceded only nine games in five matches - a record in Australia. She is returning to the Qatar Open for the first time since 2008 when she won her second title in Doha.
"I played good tennis," Sharapova said of the Australian Open. "Certainly not in my last match. I wish I would have done a few things differently, but that's the past."