Top-seeded Taylor Fritz got his North American hard-court season off to a strong start by hitting 11 aces and saving the only break point he faced in a 6-3, 6-2 victory over Aleksandar Vukic at the DC Open on Wednesday.
Fritz is coming off a semifinal run on the grass of Wimbledon.
He will be trying to replicate last year's strong showing in this portion of the season, when he reached his first Grand Slam final at the US Open.
After getting a first-round bye, Fritz now will play in the third round against Matteo Arnaldi, who eliminated No. 16 Lorenzo Sonego 7-5, 7-5.
Seeded men advancing included No. 7 Alex De Minaur, No. 8 Daniil Medvedev, No. 9 Flavio Cobolli, and No. 11 Jiri Lehecka.
No. 5 Andrey Rublev was a 7-5, 6-2 loser against 19-year-old American Learner Tien, and No. 10 Alexei Popyrin was defeated by qualifier Wu Yibing 7-5, 5-7, 6-3.
Tien has four wins over opponents ranked in the top 10 this season.
The Associated Press contributed to this report.