Simona Halep, a three-time runner up in Cincinnati, claimed her first win since May by overcoming Magda Linette 6-4 3-6 6-0.
The 12th seed has just returned from a calf muscle tear which saw her miss the French Open and Wimbledon, and was defeated by Danielle Collins in Montreal last week.
However, at 1-4 down in the second set she required medical attention for what she described as a "sharp pain" in her right leg, but after a rain delay, the Romanian came out of the blocks to claim a third-set bagel.
Halep progressed to the Round of 32 where she will play American Jessica Pegula.
SI-MO-NA
— Western & Southern Open (@CincyTennis) August 17, 2021
In her first win since May, @Simona_Halep defeats Linette 6-4, 3-6, 6-1#CincyTennis pic.twitter.com/Ax9r85ju0A
Sunday's breakthrough National Bank Open winner Camila Giorgo was beaten in straight sets by Pegula 6-2 6-2.
Former world number one Victoria Azarenka needed only one hour and nine minutes to dispose of Ludmilla Samsonova and seal her spot in the last 32.
The Belarussian triumphed 6-2 6-3 over the Russian, dominating her first serve and breaking Samsonova five times throughout the match.
Tokyo 2020 gold medalist Belinda Bencic eased past Marketa Vondrousova 6-3 7-5 continuing her bright recent run, winning in one hour and 27 minutes.
In the final match of the day's play, Caroline Garcia defeated 2017 U.S. Open champion Sloane Stephens 7-6 (9-7) 4-6 6-4 in two hours and 33 minutes.
Dayana Yastremska, Bernarda Pera, Karolina Muchova, Ons Jabeur, Elena Rybakina, Veronika Kudermetova and Coco Gauff were all winners too.
Vika roar activated @vika7 takes the opening set, 6-2!#CincyTennis pic.twitter.com/6YsZkRFM2C
— wta (@WTA) August 18, 2021
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