BELGRADE, Serbia (AP)—Novak Djokovic outlasted John Isner 7-5, 3-6, 6-3, 6-7(6), 6-4 in an epic encounter as Serbia beat the United States in the first round of the Davis Cup on Sunday.

Djokovic’s victory came despite 24 aces from Isner and gave Serbia an unassailable 3-1 lead against the 32-time Davis Cup champion. In the last rubber, Sam Querrey beat Viktor Troicki 7-5, 6-2 to make the final score in the match 3-2.

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It’s the first time since 2005 that the U.S. has been beaten in the first round and also the first time that Serbia has made it past the first round in the World Group.

Serbia will now play its quarterfinal against bitter Balkan rival Croatia.

Djokovic, ranked No. 2 in the world, needed 4 hours and 16 minutes to prevail over the 20th-ranked Isner, who was making his Davis Cup debut for the depleted U.S. team which played without both Andy Roddick and James Blake for the first time since 2000.

“Isner fought like crazy, and his serve was unbelievable,” Djokovic said of the 6-foot-9 American. “His serves are coming like from the fourth floor, and I had no idea where they would go.”

Struggling to contain Isner’s booming serve, Djokovic smashed his racket in the second set and received a ball violation penalty in the fourth set tiebreaker. The Serb then wasted three match points while leading 5-3 in the fifth set, and then two more in his next service game before finally converting his sixth match point after Isner played a forehand into the net.

“I knew I had to play my best tennis to have a chance against Djokovic,” Isner said. “He returns the serve real well, and my hat’s off to him for the victory.”

“I double-faulted on two important break points and that’s what probably cost me the match,” Isner said. “Four hours is a lot of tennis, and I’m proud how I played.”

Troicki defeated Isner in the opening singles on Friday and Djokovic beat Querrey to give Serbia a 2-0 lead. Isner and Bob Bryan pulled one back for the U.S. by defeating Nenad Zimonjic and Janko Tipsarevic in Saturday’s doubles.