Fourth-seeded Milos Raonic hit 17 aces as he beat Spaniard Pablo Carreno Busta 7-6 (5), 6-4 on Tuesday to reach the third round of the Paris Masters.
The big-serving Canadian has been hampered by a recent right ankle injury that forced him to withdraw ahead of his China Open semi-final three weeks ago.
Since then, he lost in the third round of the Shanghai Masters and in the first round of the Swiss Indoors last week.
But he was moving freely as he beat Carreno Busta for the third time in as many career meetings – all of them this year.
"The ankle is improving. I still have it wrapped up for safety," Raonic said. "But it's not really causing any nuisance."
Neither player faced a break point in the first set. At 5-5 in the tiebreaker, Carreno Busta patted a return into the net and Raonic sealed the set with an ace.
He secured the only break in the second set when his opponent scooped a low shot into the net from the baseline.
Raonic, a runner-up here to top-ranked Novak Djokovic two years ago, sealed victory with consecutive aces.
"It's always important for me to serve well," Raonic said. "I haven't served that well this summer, this hard court swing."
Earlier, Tomas Berdych avoided another early exit by beating Joao Sousa 6-3, 3-6, 7-5 to reach the third round.
At 4-4 in the deciding set, Berdych trailed 15-40 and saved two break points.
Although Berdych won the Shenzhen Open in China last month, the Czech player's form dropped sharply with first-round exits at the Japan Open and the Erste Bank Open in Vienna. In between, there was a second-round loss at the Shanghai Masters.
Losing so many ranking points forced Berdych out of the top 10 for the first time since reaching the 2010 Wimbledon final. It also leaves him needing to reach the semi-final in Paris to have a chance of qualifying for the season-ending ATP final in London – a difficult task considering he could face Andy Murray in the quarter-final.
"If you don't play your best, you don't really deserve to be there," Berdych said. "Luckily, I'm healthy. Who would have said that I'd be answering questions about London when I was in the hospital in Cincinnati? This is a nice bonus."
Berdych was referring to the appendicitis that forced him out of this year's U.S. Open.
Even though his play looked patchy at times against Sousa, at least his serving was strong with 14 aces, including a couple of booming ones on second serve.
Berdych is hopeful that working with coach Goran Ivanisevic – the big-serving Croat who won Wimbledon in 2001 – will help improve his game.
"I like his approach and how he tries to simplify things for me," the 31-year-old Berdych said. "Hopefully I can get to the point where I can start to use his experience in all the big matches he's played."
Berdych, the 2005 Paris Masters champion, nexts face either 10th-seeded Roberto Bautista Agut or Gilles Simon.
Seven players are vying for the two remaining spots in London.
Dominic Thiem and Marin Cilic, who won the Swiss Indoors, held the last two places before this week. David Goffin, Jo-Wilfried Tsonga, Lucas Pouille and Bautista Agut are the other contenders playing in Paris.
John Isner reached the second round by beating Mischa Zverev 7-6 (8), 6-4.
He will next play 15th-seeded David Ferrer, who has beaten the big-serving American seven times in eight meetings. Isner's only win, however, was in the quarter-final in Paris five years ago.
Jack Sock; Feliciano Lopez; Nicolas Mahut; Viktor Troicki, Ivo Karlovic and Gilles Muller all advanced to the second round.
Muller faces Djokovic on Wednesday.