Serbia's Novak Djokovic returns a shot to Germany's Tommy Haas in their men's singles fourth round match at the Sony Open tennis tournament in Key Biscayne, Florida March 26, 2013.  [Photo/Agencies]

BOISE, Idaho - Novak Djokovic believes he has left his recent poor form behind and will be in top shape when he leads Serbia in this weekend's Davis Cup quarter-final tie against the United States.

The world number one, who was upset last month in the semi-finals at Indian Wells by Juan Martin Del Potro and then in the third round at Miami by Tommy Haas, will open Friday's play against American number two John Isner.

That match will be followed by a clash between top American Sam Querrey and Serbia's number two, Victor Troicki.

Djokovic said that he played the worst that he has in three years in his 6-2 6-4 loss to Haas.

"You got to be ready to win and lose," Djokovic told reporters. "I've been very consistent in the last few years of my career. I understand that people are always expecting me to play semi-finals or finals of every event I play in. If a loss 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."

The tie marks just the second meeting between the U.S. and Serbia in Davis Cup. Serbia won the only meeting, 3-2, in the 2010 in Belgrade.

The United States picked an indoor hard court in Boise, Idaho, partly because of its high altitude - 2,842 feet (866 meters) above sea level - which should benefit Isner and Querrey, both of whom are big servers.

"We are playing in the conditions which are not normal for the tennis," said Serbian captain Bogdan Obradovic. "Still, we practice for five days and also doing some fitness. So my players are ready."

US captain Jim Courier is hoping that Isner and Querrey can turn around their recent fortunes.

The 20th ranked Querrey has not reached a quarter-final since early February, while number 23 ranked Isner is 7-7 this year and failed to close out the U.S. Davis Cup tie in February against Brazil, leaving Querrey to clinch the final rubber.

Isner has beaten Djokovic once, but is 1-2 against the Serbian.

"I have to play very well," Isner said. "If I don't, chances are it may not turn out so good for me.

"He's the number one player in the world. Everyone has to play well if they want to have a chance to beat him. Simple as that."

While Saturday's doubles is scheduled to be between the world's top team of Bob Bryan and Mike Bryan against Nenad Zimonjic and Ilija Bozoljac, Courier expects Troicki to play doubles with Zimonjic, as they have teamed together many times in the past.

The Bryans are 21-3 as a doubles team together in Davis Cup, but lost their last match against Brazil.

"We're itching to go and want to redeem ourselves," Mike Bryan said. "We think we can play better, so that's why we're excited for this one."

Should the tie go to Sunday singles, Djokovic is scheduled to play Querrey in the first match, followed by Troicki versus Isner.

The No. 44-ranked Troicki could then be called upon to play three rubbers, which he has never done so in the 14 ties he has played.

"Personally I feel fit and ready to play all three days if I have to," Troicki said.