The No. 1 ranking on both tours is up for grabs at the Australian Open. Roger Federer has a slim chance to dethrone Novak Djokovic, while Maria Sharapova and Serena Williams are gunning for current No. 1 Victoria Azarenka.
For the men, Djokovic can retain No. 1 by beating Tomas Berdych in Monday's quarterfinals. If he fails to do so, Federer can retake the top spot by winning the title. Sorry, Andy Murray. You're not part of this conversation yet.
The scenarios are a bit more complicated for the women, though by virtue of her fourth-round exit here last year, Williams is in the best position. She can take the top spot for the first time since 2010, a span that's seen her come back from toe surgery and the resultant complications in 2011.
Here are the cleanest scenarios for the women's No. 1:
Azarenka: Win the Australian Open.
Williams: Make the final or make the semifinals as long as Sharapova doesn't win the title.
Sharapova: Win the title or lose in the final as long as Williams loses in the quarterfinals and Azarenka doesn't win the title.