MASON, Ohio — Top seed Simona Halep returned to sew up victory over Ajla Tomljanovic on Thursday after their second round match at the Cincinnati Open had been suspended the previous day due to rain, while reigning US Open champion Sloane Stephens was knocked out in the third round by Elise Mertens.

Stephens, seeded third, fell to the 15th seeded Belgian 7-6(9-8) 6-2 and failed to reach the quarterfinals for the third time in her past four events.

German fourth seed Angelique Kerber was also upset, going down 2-6, 7-6(7-3), 6-4 to American Madison Keys, while Aryna Sabalenka beat sixth seed Caroline Garcia 6-4, 3-6, 7-5.

Keys recorded 55 winners to beat Kerber, a rare victory over the German who has come out on top in seven of their nine meetings. "Considering the last — what was it, six times? — it didn't go so hot, this victory feels good,” Keys said.

"More than anything, it was just how I handled being down and not letting the previous results kind of spiral in my head for me. I think that's what I'm happiest with.”

Halep had been two games away from reaching the third round when rain interrupted her match against Australian Tomljanovic on Wednesday, and while the conclusion was delayed again for about four hours on Thursday the Romanian wasted little time wrapping it up when she got the chance, sealing it 4-6, 6-3, 6-3.

Halep had been due to play her third-round match on Thursday against another Australian, Ashleigh Barty, but that has been postponed until Friday.

Halep owns a 1-0 career record against Barty, with the win coming last week in the semi-finals at Montreal where the French Open champion went on to capture her third title of the season.

Kiki Bertens and Anett Kontaveit had their match suspended due to rain. Bertens took the first set 6-3 and Kontaveit led 4-1 in the second when play was halted. — Reuters