Note: You can find the full order of play for today's matches - as well as live stream links - on our schedule page.
Here's what to look for on day four of tennis at the Rio Olympics:
Keys takes the first set from Navarro.
Spain's 7th-seeded David Ferrer, who's quickly becoming a medal favorite in singles, takes on Russia's Evgeny Donskoy on court 1 now.
The U.S.' Madison Keys has taken to Court 1 and is already up a game on Spain's Carla Suarez Navarro.
Keys is seeded 7th while Suarez Navarro is seeded 9th.
Check out Keys' victory from yesterday, as well as the live stream: