BIRMINGHAM: Jack Sock and John Isner gave the United States a sweep of Friday's 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. Isner dropped the first set before rebounding to beat Henri Laaksonen 4-6, 6-2, 6-2, 7-6 (1).

Switzerland was without the country's two best players: 18-time Grand Slam champion Roger Federer and three-time major champ Stan Wawrinka. Federer won the Australian Open on Sunday night.

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."

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 quarter-finals against Australia with a win.

Querrey is ranked 27th, Johnson 31st. Bossel is 485th and Bellier No. 598.

Sock says the US team isn't taking anything for granted.

"Davis Cup, anything can happen," he said. "You see it every year. Every tie almost you see some kind of crazy things happen."