Belgrade, Serbia (Best E Casino) - Novak Djokovic outlasted big John Isner in five sets on Sunday to lift Serbia past the United States and into the 2010 Davis Cup quarterfinals.

The Serbs wound up with a 3-2 victory in the best-of-five showdown at Belgrade Arena.

The world No. 2 Djokovic got everything he could handle from the 6-foot-9 Isner in the first reverse singles rubber, as the former Australian Open champion barely snuck out a 7-5, 3-6, 6-3, 6-7 (6-9), 6-4 decision on the Americans' least-favorite surface, red clay. The Djokovic win gave the hosts an insurmountable 3-1 lead.

"Isner fought like crazy, and his serve was unbelievable," Djokovic said of the 20th-ranked American. "His serves are coming like from the fourth floor, and I had no idea where they would go."

Djokovic needed six match points, but finally prevailed in 4 hours, 16 minutes against Isner, who made his Davis Cup debut with a singles loss against Viktor Troicki here on Friday and was a doubles winner on Saturday.

"Four hours is a lot of tennis, and I'm proud how I played," Isner said after succumbing to Djokovic.

In Sunday's dead rubber, Sam Querrey cruised past Troicki 7-5, 6-2.

The Serbs, who will appear in their first-ever Davis Cup quarterfinal, will battle Croatia in July.

On Saturday, an American doubles team of Isner and Bob Bryan got the United States on the scoreboard (1-2) with a clutch four-set doubles victory over a Serbian tandem of Janko Tipsarevic and Nenad Zimonjic. Bryan played without his twin brother Mike on Day 2, as the towering Isner was a late substitute after Mike fell ill due to some food poisoning.

The triumphant Serbs are captained by Bogdan Obradovic, while Team USA is led by Patrick McEnroe, who guided the U.S. to a record 32nd Davis Cup title in 2007.

The Americans have now been relegated to World Group playoffs, as they'll have to qualify for the 2011 World Group.

The U.S. played without its top gun this week, Wimbledon runner-up Andy Roddick, who decided against playing in the prestigious international team event this year.

This marked the first-ever Davis Cup meeting between Serbia and the U.S.