Main draw play began Monday with a full slate of first round action.
Starting off the day's play was Cincinnati native Caty McNally. The 17-year-old came into her first Western & Southern Open main draw one week removed from her first WTA semifinal in Washington, D.C.
McNally opened against Elise Mertens, a W&S Open quarterfinalist last year. Mertens defeated McNally 7-5 6-0.
While wild card, McNally, was defeated, Venus Williams was a 7-5 6-2 winner over Ohio native Lauren Davis. The win by Williams sets up a second round match with defending champion Kiki Bertens.
An early men’s upset came on Grandstand when Radu Albot defeated 2016 W&S Open champion Marin Cilic 6-4 7-6(6).
Andy Murray's return to singles action ended in a straight sets loss to 2015 W&S Open quarterfinalist Richard Gasquet. Murray had not played singles since January when he underwent a hit resurfacing operation following the Australian Open. Gasquet's 6-4 6-4 win sets him for a second round clash with No. 4 seed Dominic Thiem.
American Sam Querrey, also a former Western & Southern Open quarterfinalist, advanced with a two tie-break win over Pierre Hugues-Herbert, 7-6(2) 7-6(1). Querrey will next face top seed Novak Djokovic on Tuesday.
Guido Pella earned his 100th career match win, defeated Casper Ruud 7-5 7-6(4).
Aryna Sabalenka, a W&S Open semifinalist last year, moved on with a 6-1 6-4 win over Petra Marctic.
Eighteen-year-old Iga Swiatek defeated Caroline Garcia 7-6(1) 6-1.
Nick Kyrgios, a finalist here in 2017, looks to be comfortably maintaining his momentum following his title run in Washington, D.C. two weeks ago. The 24-year-old Australian completed a 7-5, 6-4 win over Italian Lorenzo Sonego in 79 minutes on Grandstand, setting up a second-round clash with No. 8 seed Karen Khachanov.
Former Western & Southern Open champion Maria Sharapova extended her perfect record over Pittsburgh native Alison Riske to 4-0 with a 6-3, 7-6(4) victory. The Russian wild card is competing in just her seventh tournament this season as a result of nagging shoulder issues.
Next up for Sharapova? Top seed Ashleigh Barty. They've played twice in the past two years, with Sharapova winning on clay in Rome in 2018 and Barty taking out the five-time major champion in three sets at the Australian Open in January.