There were also wins for Kyrgios, Coric, Goffin, Chung, Raonic, and Shapovalov
Roger Federer 'feeling good' after winning on return to Cincinnati Masters
Roger Federer said he has "turned the page" after winning on his return to action at the Cincinnati Masters on Tuesday.
Federer, 37, is pacing his season, playing a limited schedule and missing events when he feels the need to rest. He has missed the last two editions of this tournament because of injury.
However, there were few signs of rust from the 20-time grand slam champion, who produced a comprehensive 6-4, 6-4 defeat of Peter Gojowczyk.
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Federer's defeat of the 47th-ranked German in 72 minutes marked the first step towards a possible eighth title at the tournament.
"I felt good in that first match, to be honest, walking out, hardly any nerves. I think I knew what I had to do," Federer said.
"It's fast-court tennis. I knew my opponent was going to go for it and take big cuts at the ball, so there is only so much you can really do.
"It's nice to have played a match so that my last match was not the Anderson match ... you've kind of turned the page. It's a good thing.
"The goal is now to recover from this match, take the positives with me. Of course the big goal is the US Open."
The contest was the first for the Swiss since losing to Kevin Anderson in five sets in the Wimbledon quarter-finals on July 11.
Eighth seed Dominic Thiem was forced to withdraw without hitting a ball, after suffering with a virus. The Austrian played just one losing match last week in Toronto on the hardcourts since making a late switch from post-Wimbledon clay.
Nick Kyrgios served 39 aces, including one to save match point, to power into the second round with a dramatic 6-7, 7-5, 7-6 win over Denis Kudla.
Last year's losing finalist finally saw off the American on his sixth match point. The Australian will next face Croatian Borna Coric, who beat Daniil Medvedev 6-2, 6-3.
Weekend Toronto finalist Stefanos Tsitsipas tired late in a 7-5, 6-3 loss to Belgian 11th seed David Goffin.
South Korea's Chung Hyeon rallied past a struggling Jack Sock for a 2-6, 6-1, 6-2 victory.
Chung handed the slumping American an eighth straight defeat, with Sock's last win coming in the opening round at Rome three months ago.
Unseeded Milos Raonic advanced past Serb Dusan Lajovic 6-3, 6-3 at the combined ATP and WTA event, the last major tune-up prior to the US Open on August 27.
In the day's final game, Canada's Denis Shapovalov defeated British 14th seed Kyle Edmund 6-4, 7-5.