Serena Williams must advance to the quarterfinals to secure the No.1 ranking.

With the top spot on the WTA rankings in play this week, World No.1 Serena took a late wildcard into the tournament. The scenarios are simple. If Serena makes the quarterfinal she will hold onto the No.1 ranking heading into the US Open. If she loses before the quarterfinal stage, No.2 Angelique Kerber can overtake her by winning the title.

A two-time defending champion here, Serena leads the top half and she could open her tournament against the woman how knocked her out of the Olympic tennis event last week: Elina Svitolina. Svitolina would have to get past Christina McHale in the first round to book a rematch with the 22-time Grand Slam champion. Serena could then play either Karolina Pliskova or Jelena Ostapenko, with Svetlana Kuznetsova or Timea Bacsinszky looming in the quarterfinals.

Click here to check out the full draw.

As for Kerber, anything less than the title means she will remain at No.2 heading into New York. She is into the Gold Medal match at the Olympics, which will be played on Saturday, but as a Top 16 seed she’ll have a bye into the second round. The question is how much will she have left in the tank?

Kerber will play either Kristina Mladenovic or a qualifier in the second round and could play either Sam Stosur or Barbora Strycova in the Round of 16.

Rio Redux.

Serena and Kvitova will both have an opportunity to avenge their Olympic losses. For Serena that could come in her first match against Svitolina, while Kvitova could play Monica Puig in her first match of the tournament. Puig, who is also into the Gold Medal match against Kerber, opens her tournament against American wildcard Louisa Chirico.

Simona Halep gets back to work.

After skipping Rio, Halep spent the week training with coach Darren Cahill and famed fitness trainer Gil Reyes. The Rogers Cup champion will look to continue her winning ways in Cincinnati. With a significant number of points on the line over the next four weeks – Halep made the final here last year and the semifinals of the US Open – defending those points would set up a significant rankings push in Asia this fall.

Halep has won 23 of her last 26 matches dating back to her title run at the Mutua Madrid Open, and she’s currently riding a 10-match win streak. The No.3 seed here, she got the toughest draw of any of the top four seeds, landing in a quarter with No.5 seed Agnieszka Radwanska. She will open her tournament against either Yulia Putintseva or a qualifier and could then face Belinda Bencic, who is returning from injury, or Caroline Garcia.

Agnieszka Radwanska has work to do.

The No.5 has not made a semifinal since April (Porsche Tennis Grand Prix) and has struggled to put together a confidence boosting run over the last few months. It won’t be easy this week in Cincinnati, where she has never made it past the quarterfinals. She will play either Andrea Petkovic or Lucie Safarova in the second round, with Johanna Konta potentially looming in the third round. All that to get to a possible quarterfinal against Halep.

The qualifying draw is stacked.

The Cincinnati qualifying draw, which begins on Saturday, would be a strong International-level event in and of itself. The main draw cut-off was at No.41, meaning a host of top notch players will have to play their way into the main draw.

Eugenie Bouchard took a wildcard into qualifying, and she’s alongside a list of exciting players like Alizé Cornet, Daria Gavrilova, Misaki Doi, Sabine Lisicki, Camila Giorgi, Sorana Cirstea and more. It will be a tough weekend of qualifying matches and the complexion of the draw could change dramatically depending on who makes it through and where they end up being placed.

Follow the qualifying draw here.

Top seeds in the top half: Serena Williams, Garbiñe Muguruza, Svetlana Kuznetsova, and Dominika Cibulkova.

Top seeds in the bottom half: Angelique Kerber, Simona Halep, Agnieszka Radwanska, and Roberta Vinci.

Projected quarterfinals: Serena Williams vs. Svetlana Kuznetsova, Garbiñe Muguruza vs. Dominika Cibulkova, Simona Halep vs. Agnieszka Radwanska, Angelique Kerber vs. Carla Suárez Navarro.

First round matches to watch: Andrea Petkovic vs. Lucie Safarova, Elina Svitolina vs. Christina McHale, Sara Errani vs. CoCo Vandeweghe, Louisa Chirico vs. Monica Puig.

Potential second round matches to watch: Serena Williams vs. Elina Svitolina, Karolina Pliskova vs. Jelena Ostapenko, Garbiñe Muguruza vs. CoCo Vandeweghe, Petra Kvitova vs. Monica Puig, Johanna Konta vs. Ana Ivanovic, Belinda Bencic vs. Caroline Garcia, Simona Halep vs. Yulia Putintseva.

All photos courtesy of Getty Images.