The depth of the WTA Tour will be on full display when main draw play kicks off on Monday. Take a look at these popcorn-worthy first-round matches.
Serena Williams vs Daria Gavrilova
Williams, a two-time Cincinnati champion, has a 2-0 record over Gavrilova, but much has changed since their last meeting in 2016. The 23-time Grand Slam champion is still working her way back after giving birth to daughter Olympia last fall. After a first-round drubbing at the hands of Johanna Konta two weeks ago in San Jose, Williams will be looking for a confidence boost.
Naomi Osaka [JPN] vs Ekaterina Makarova [RUS]
One of the most electrifying young players on the WTA tour, Osaka announced her arrival when she captured her first career title at Indian Wells this year. The 20-year-old will have a first-round challenge in the form of upset specialist and former world No. 8 Makarova. It will be the first meeting between the two.
 Karolina Pliskova [CZE] vs Agnieszka Radwanska [POL]
After struggling with injury over the past year, Agnieszka Radwanska is in search of a breakthrough. When she opens play in Cincinnati, world No. 9 Karolina Pliskova will be standing in her way. But here’s a stat to keep in mind: Radwanska holds a 7-0 head-to-head record against the 2016 Cincinnati champion. Upset alert?
 Venus Williams [USA] vs Maria Sakkari [GRE]
Serena isn’t the only Williams sister with tricky first-round matchup. Venus, 38, will face Sakkari just two weeks after losing to the red-hot 23-year-old in San Jose. Sakkari, currently sitting at her career-high rank on No. 31 in the world, will be making her Western & Southern Open main draw debut.
Honorable Mention: Marketa Vondrousova vs Ashleigh Barty, Bethanie Mattek-Sands vs Madison Keys, Kiki Bertens vs CoCo Vandeweghe