RIO DE JANEIRO, Brazil – The top three seeds will battle for quarterfinal slots on Day 4 of the Rio Games. Chris Oddo breaks down the key Olympic match-ups at wtatennis.com.

Tuesday, Third Round

Centre Court
[7] Madison Keys (USA #9) vs. [9] Carla Suárez Navarro (ESP #12)
Head-to-head: Keys leads, 2-0
Key Stat: Keys played the longest match of this year’s Olympic Games on Monday, taking out Kristina Mladenovic in three hours and 14 minutes.
Madison Keys is one of the few players in Rio who has a big enough game to hit through the slow-playing hardcourts. She’ll have to do just that and then some if she intends to get past the gritty Carla Suárez Navarro on Tuesday. Keys won the pair’s two previous meetings, but both of them have gone three sets. If Keys is going to make it three in a row against the Spaniard, she’ll have to do what she could not against Simona Halep in the Montréal final. In that match Keys struggled to win the longer rallies and didn’t serve well enough to keep the majority of points short. Against a deft baseliner like Suárez Navarro, who defeated Ana Konjuh, 7-6(5), 6-3 on Monday, Keys will have to avoid making this match a physical encounter. After three hours and 14 minutes in the Rio heat on Monday, will Keys have the energy left to execute her game plan?

Pick: Suárez Navarro in three

[1] Serena Williams (USA #1) vs. Elina Svitolina (UKR #20)
Head-to-head: Williams leads, 4-0
Key Stat: Williams is bidding to be the first Woman in history to successfully defend an Olympic singles title.
In her Olympic debut, Elina Svitolina has reeled off back-to-back three-set victories, over Andrea Petkovic and Heather Watson, to book her spot in the sweet 16. But the World No.20 will run into a much stiffer challenge on Tuesday when she faces defending Olympic gold medalist Serena Williams. The last four meetings between Svitolina and Williams have seen Svitolina gain some moral victories, but the truth of the matter is that her defensive approach leaves her far too vulnerable against an offensive juggernaut like Williams. Will Svitolina step out of her shell and try to take the game to Williams, or will the Ukrainian be content to leave the match on Serena’s racquet in the hopes that the mighty American might falter? Williams struggled against Alizé Cornet on Monday, but eventually prevailed in straight sets. She could be tested by Svitolina on Tuesday, but expect Williams to sharpen her focus as the medal rounds draw nearer.

Pick: Williams in two

Court 1
[2] Angelique Kerber (GER #2) vs. [13] Samantha Stosur (AUS #17)
Head-to-head: Tied, 3-3
Key Stat: Kerber is bidding to become the first German woman to win a medal at the Olympics since Steffi Graf in 1992.
How impressive has Angelique Kerber’s 2016 been? A maiden Grand Slam title and a Wimbledon final have thrust the cagey German close to the top of the rankings and she’s gunning for more precious hardware here in Rio. Kerber made relatively light work of Canada’s Eugenie Bouchard on Monday and appears to be primed for another deep run in this her coming-of-age season. But standing in her way on Tuesday will be the determined Sam Stosur, a player who is tailor-made for the gritty, slow-paced Rio hardcourts. Stosur has done most of her damage on clay this year, but she just might have a shot to upend Kerber if she can dictate with her serve and play without fear in the pair’s seventh career meeting. Stosur was strong in her straight-sets victory over Japan’s Misaki Doi on Monday, but she’ll have to be even stronger if she hopes to snap her three-match losing streak to Kerber on hardcourts.

Pick: Kerber in three

Court 2
[3] Garbiñe Muguruza (ESP #4) vs. Monica Puig (PUR #34)
Head-to-head: First Meeting
Key Stat: Neither player has dropped a set this week in Rio.
It looks like Garbiñe Muguruza is turning the page on a disappointing grass court season and reverting back to the elite form that saw her claim her maiden Grand Slam title at Roland Garros this spring. It may seem like a long time ago, but Muguruza’s performance in Paris left no doubt about her talent, mindset and belief. Now the challenge is to be more consistent. Muguruza, who plastered Japan’s Nao Hibino, 6-1, 6-1, on Monday, is the only seeded player left in her quarter. This is a tremendous opportunity for the Spaniard to open her hardcourt season in style, but she’ll have to get past the dangerous Monica Puig to keep her medal hopes alive. Puig has had a successful season on all surfaces, but the Puerto Rican has had very little experience against the WTA’s elite. She’s only played five Top 10 players in her career, losing four. Can she send a message and create a stir with a big upset in Rio?

Pick: Muguruza in three

Around the grounds…
Great Britain’s Johanna Konta’s magical season continues in Rio. The 25-year-old has yet to drop a set ahead of her round of 16 encounter with Svetlana Kuznetsova. But she’ll be tested in a big way by the resurgent Russian when the pair meets for the first time on Tuesday. Doubles action will also take center stage on Tuesday, as Garbiñe Muguruza, Carla Suárez Navarro, Sara Errani, Kirsten Flipkens, and Ekaterina Makarova will all pull double duty.

By the numbers…
19 – The age of Russia’s Daria Kasatkina, who is the youngest player left in the draw. Kasatkina will face Italy’s Sara Errani on Day 4. The Italian defeated Kasatkina in three sets in their only previous meeting.
11-1 – Serena record in Olympic singles matches. If she wins the title, Williams will tie Steffi Graf (15-1) for the most Olympic singles victories of all-time.
3 – Russia leads the way with three players (Kasatkina, Makarova, Kuznetsova) into the round of 16. The United States, Spain and Germany each have two alive in the draw, with 11 nations represented in total.
1 – Number of Olympic singles champions remaining in the draw (Serena).