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.