Marin Cilic started his Rogers Cup campaign with a three-set win over Denis Istomin.
Croat Cilic, the 15th seed, prevailed 6-2 4-6 7-5 against his Uzbek opponent to advance to the second round of the Masters 1000 event in Toronto.
It was a good day for a trio of Frenchmen; Jo-Wilfried Tsonga, Jeremy Chardy and Benoit Paire all claiming first-round wins.
Tsonga, the 13th seed, downed his compatriot Edouard Roger-Vasselin 7-6 (7/3) 6-1. while Chardy saw off Argentina's Federico Delbonis 6-3 5-7 6-4 and Paire overcame Colombian Alejandro Falla 6-7 (3/7) 6-4 6-2.
There was disappointment for 10th seed John Isner and 14th seed Roberta Bautista Agut, who both crashed out on Monday.
Croat Ivan Dodig outlasted Isner 6-4 6-7 (4/7) 6-3 and Bautista Agut was beaten in straight sets, 7-6 (9/7) 6-3, by fellow Spaniard Felciano Lopez.
Britain's Andy Murray, who won this event in 2009 and 2010, has a first-round bye after world No 2 Rafael Nadal's withdrawal bumped him up into the top eight seeds.
Watch the Toronto Masters all week on Sky Sports 3.