Marin Cilic of Croatia defeated Denis Istomin of Uzbekistan 6-2, 4-6, 7-5 Monday on the opening day of the Rogers Cup in Toronto.
Cilic, seeded 15th, will play the winner of an afternoon match between Guillermo Garcia-Lopez and Marinko Matosevic in the second round of this U.S. Open tuneup.
France's Jeremy Chardy beat Argentina's Federico Delbonis, 6-3, 5-7, 6-4.
Tenth-seeded John Isner faces Ivan Dodig later in the day.
On the women's side, Sabine Lisicki upset 13th-seeded Sara Errani 6-1, 7-5 in the first round.
Errani, the 2012 French Open runner-up, is most comfortable on clay, while the 29th-ranked Lisicki likes the faster surfaces. Lisicki, the 2013 Wimbledon runner-up, hit the fastest recorded serve in WTA history (131 mph) last week at Stanford.
Errani was serving for the second set at 5-3 but let the lead slip away. Lisicki next plays Svetlana Kuznetsova or Madison Keys.
Barbora Zahlavova Strycova beat Roberta Vinci 7-5, 7-5. Zahlavova Strycova will face third-seeded Agnieszka Radwanska.
American qualifier Shelby Rogers defeated Ajla Tomljanovic 6-4, 7-6 (5) to set up a second-round meeting with the star attraction of this year's event, fifth-seeded Eugenie Bouchard of Westmount, Quebec. That match is expected to be played Tuesday night.
Alize Cornet beat qualifier Lauren Davis 6-3, 7-5 and will next face eighth-seeded Victoria Azarenka.
Klara Koukalova beat Dutch qualifier Kiki Bertens 7-5, 7-6 (5).
