Fernando Verdasco faced a tough opening to his Atlanta Open campaign against Serbian Dusan Lajovic but managed to progress after a topsy-turvy first set.
Neither player could break in the first set as Verdasco had to win a tie-break on the way to a 7-6 (7-2) 6-4 victory to book his spot in the next round.
Three seeds were in action but just two progressed with the Spaniard joined by eighth seed Taylor Fritz in the second round.
Fritz knocked off Austin Smith 6-2 6-2 in just over an hour, serving seven aces in what proved an easy win.
Sixth seed Guillermo Garcia-Lopez was the sole seeded player to exit as he lost his match against Argentinean Horacio Zeballos.
Garcia-Lopez sent down seven aces, but had eight double faults in a 6-3 6-7 (5-7) 6-4 loss.
Elsewhere, Bjorn Fratangelo beat Igor Sijsling 6-1 7-6 (7-2), Yoshihito Nishioka won a tight affair against Daniel Evans 6-2 6-7 (2-7) 7-6 (7-4), Tobias Kamke won 7-6 (9-7) 7-6 (7-2) against Sergiy Stakhovsky and Julien Benneteau beat Australian qualifier John-Patrick Smith 6-4 6-2.