Melbourne - Towering John Isner cruised to a straight-sets victory over Sam Groth to give the United States a 1-0 lead in the Davis Cup World Group tie at Kooyong on Friday.
The world number 11's serve was too strong for the 77th-ranked Groth, winning 7-6 (7/2), 6-2, 6-2 in one hour 49 minutes on the grass surface.
Isner served his way out of three break points down in the first set to confidently take the opening set in a tiebreaker 7-2.
The beanpole American smashed 20 aces as Groth's game deteriorated and posed an early dilemma for new Australian captain Lleyton Hewitt.
The retired Hewitt is on standby for a possible playing appearance following the match-eve withdrawal of star youngster Nick Krygios with a virus and back trouble.
Isner, 30, took his year's win-loss record to 5-4 while Groth slumped to 1-7 in his first meeting with the 2.08 metre tall American.
Bernard Tomic was attempting to keep Australia in the tie in Friday's second singles match against Jack Sock.
"I am extremely satisfied with that win. I played exceptional tennis in the second and third sets," Isner said.
"The first set could have gone either way, I was 0-40 down at 2-2 and those three points were essentially set points and to save that and climb out and play a great tiebreaker gave me a lot of momentum from that point on."
Isner said he did a good job to quieten the capacity Australian crowd with his serving.
"I think I did a great job holding on to my serve and not giving them much to cheer about when I was playing short points on my serve that sort of drowned the crowd out," he said.