Japanese eighth seed Go Soeda had to come from a set down before seeing off Belgium's Xavier Malisse in the ATP BB&T Atlanta Open.
The first-round match was suspended for more than two hours at 2-2 in the first set due to rain and Malisse initially looked to be coping better with the disruption when he clinched the first set.
But Soeda went on to post a 4-6 7-5 6-4 victory in two hours 32 minutes to set up a second-round meeting with Russia's Igor Kunitsyn.
Michael Russell also came from a set down to oust fellow American Alex Kuznetsov 2-6 6-4 7-6 (7/4). He will next face South African fifth seed Kevin Anderson.
In another all-American encounter, James Blake was a 1-6 6-3 7-5 winner against sixth seed Ryan Harrison. Blake will take on Matthew Ebden in the second round after the Australia battled past Ukrainian qualifier Sergei Bubka 5-7 6-1 6-1.
Belgian qualifier Ruben Bemelmans will face top seed John Isner after ousting American Rajeev Ram 6-1 6-3, while Lithuanian qualifier Ricardas Berankis saw off Russia's Dmitry Tursunov 6-3 6-2.
The top four seeds - Isner, Mardy Fish, Kei Nishikori and Andy Roddick - all received first-round byes.