Jack Sock and John Isner gave the United States a sweep of Friday's (Saturday AEDT) singles matches in a first-round Davis Cup tie against Switzerland.
Sock, the world's 20th-ranked player, defeated No.146 Marco Chiudinellli 6-4 6-3 6-1 in the first match at Legacy Arena.
Sock said he started out playing tentative but got a lift from an early service break.
"There are always a few extra nerves, I think, playing Davis Cup," he said. "When you're playing for your country, being a part of a team, maybe at a normal event, normal tournament, you come out swinging a little bit more.
"I think I was a little hesitant at the beginning. Maybe too conservative playing when obviously my game is to kind of play big and hit big forehands and be aggressive."
Isner dropped the first set before rebounding to beat Henri Laaksonen 4-6 6-2 6-2 7-6 (7-1).
In Saturday's doubles match, Sam Querrey and Steve Johnson play Antoine Bellier and Adrien Bossel. The US would secure the victory and advance to the April quarterfinals against Australia with a win.