Top seed Tommy Haas and eighth seed Lleyton Hewitt breezed into the second round at the Delray Beach Open on Tuesday.
World No 12 Haas, who won the tournament in 2006, took just less than an hour to dispatch American qualifier Wayne Odesnik 6-2 6-1.
The German will now face US qualifier Steve Johnson, who defeated Kazak Mikhail Kukushkin 6-4 6-3, in the second round.
Australian Hewitt was equally as swift, ousting American Bradley Klahn 6-3 6-1 with compatriot and golf legend Greg Norman watching from the stands.
Hewitt, who now has 598 ATP tour match wins, will next face fellow Aussie Marinko Matosevic, who downed Belgian David Goffin 6-2 6-4.
Meanwhile, Lu Yen-Hsun was forced to retire after winning his first set 6-4 against Ryan Harrison.
Harrison will next meet Russian Teymuraz Gabashvili, who rallied to beat Australian Matthew Ebden 2-6, 6-3, 6-2.
South African fourth seed Kevin Anderson, who lives in Delray Beach, reached the second round by fighting back to beat American Tim Smyczek 4-6 6-1 6-3.
Next in Anderson's path is Ivo Karlovic, who opened with a 7-6, 6-3 victory over Samuel Groth.
Second seed John Isner recovered from a slow start to progress with a 4-6 7-6 (7-3) 6-4 over fellow American Michael Russell.