Former finalist John Isner edged into the Western & Southern Open second round, while Alex de Minaur also moved through on Sunday.
Isner, runner-up in 2013, was pushed before the 13th seed overcame Dusan Lajovic 7-6 (7-3) 1-6 7-5 at the ATP Masters 1000 event.
The American has endured a tough start to the hard-court swing in North America, winning just two of five matches heading into the tournament in Cincinnati.
Isner served 27 aces to get past Lajovic and will face either Pablo Carreno Busta or Gilles Simon in the second round.
De Minaur also progressed thanks to a 6-7 (5-7) 6-1 6-2 victory over Italian Marco Cecchinato.
The Australian will meet either Croatian 12th seed Borna Coric or American wildcard Reilly Opelka.Published 12 Aug 2019, 07:42 IST