Fourth-seeded Milos Raonic hit 12 aces and saved all five break points he faced as he beat Steve Johnson of the United States 7-6 (4), 6-4 in the first round of the Swiss Indoors on Tuesday.
Johnson, who did not face a break point in the first set, saved one on his opening service game in the second set, where he also missed four chances to break Raonic's serve.
The 1.95-meter Canadian sealed victory by breaking Johnson's serve for the first time in the 10th game. He next faces another American, Donald Young.
Meanwhile, eighth-seeded Ivo Karlovic had 23 aces as he advanced to the second round with a 7-6 (4), 6-3 win against Lukas Rosol. The 35-year-old Karlovic won 95 percent of his first-serve points and next plays Frenchman Kenny De Schepper, who beat Argentina's Federico Delbonis 7-6 (3), 7-5.
In other first-round action, German Benjamin Becker needed just over one hour to breeze past qualifier Gastao Elias of Portugal 6-3, 6-2. He next faces either third-seeded Stanislas Wawrinka of Switzerland or Kazakhstan's Mikhail Kukushkin, who played later Tuesday.
Croatia's Ivan Dodig needed nearly three hours to get the better of Swiss wild card Marco Chiudinelli 6-4, 6-7 (7), 6-4 and next plays seventh-seeded David Goffin of Belgium.
Top-seeded Roger Federer and No. 2 Rafael Nadal, who struggled with appendicitis earlier this month in Shanghai, are in second-round action on Wednesday.
Federer, a recent winner in Shanghai, faces Luxembourg's Gilles Muller and Nadal takes on unheralded Frenchman Pierre-Hugues Herbert, a qualifier ranked 120th.