Novak Djokovic says he has been practicing well this week in Boise and feels fresh after posting sub-par results during the American spring hard-court season. Djokovic will lead Serbia against the U.S. Davis Cup team in Idaho this weekend.

After winning the Australian Open and Dubai titles, Djokovic was upset by Juan Martin Del Potro at Indian Wells before losing to Tommy Haas in Miami.

“I played, I think, the worst match that I had in the last three years.” Djokovic said of the loss to Haas. “But I had more time to prepare here. I arrived Saturday night actually, so I've been practicing for five days. The conditions are quite different. I never played on such an altitude now for three consecutive days. It's going to be definitely tough for all of us. It's a big challenge for both U.S. and Serbian teams.”

Djokovic will open Friday’s play against John Isner and the World No. 1 concedes expectations are high.

“You got to be ready to win and lose,” Djokovic said. "I've been very consistent in the last few years of my career. I understand that people are always expecting me to play semifinals or finals of every event I play. If I lose before that stage of the tournament happens, everybody starts questioning.  I'm feeling good. I'm moving on. I'm trying to play well here, and hopefully we can bring the win to Serbia.”