Top American Sam Querrey picked a good time to pull off his first five-set Davis Cup victory when he stopped Victor Troicki 7-6 3-6 4-6 6-1 6-4 to level the United States' tie against Serbia 1-1.
Querrey's victory boosted the hosts after world number one Novak Djokovic earlier raced past John Isner 7-6 6-2 7-5.
Querrey, who just took over the top American ranking last month, looked tired and without confidence after Troicki won the second and third sets.
But with the charged-up crowd screaming in his ears, Querrey revived and powered through the fourth set before a tooth and nail battle for the fifth.
Querrey fought off two break points in the fourth game of the deciding set, and then broke the Serbian to 5-4 with a big forehand return that Troicki couldn't lift over the net.
The American then served out the match to love, ending it with a forehand winner on the run and a big serve.
"I'm a pretty mellow player generally and the crowd was awesome today," Querrey told reporters.
"Winning that fourth set, they're on their feet and cheering. Then that fifth set, every game on my serve, on Troicki's serve, when it was a 30-all or deuce, they were loud and vocal, and it helped a lot."
Djokovic started off slowly against Isner and was broken in the third game when he double faulted twice, but the tall American handed the break back in the sixth game when he committed three straight unforced errors.
The two went into a tiebreaker where the big serving Isner usually flourishes, but he committed a key forehand error when serving and went down 2-0.
Djokovic successfully rode the lead to take the tiebreaker 7-5 when he deceived the American with an off-speed serve.
Djokovic played more aggressively after that and flew about the court, decisively winning the last 12 points of the match.
"These kind of matches are very intense and there is a lot at stake," said Djokovic, who finished the match with 24 winners and 10 unforced errors.
"You're playing for your country. You get more involved with the emotions and you really want to start well; you want to bring the first point to Serbia."
Djokovic was not originally scheduled to play doubles on Saturday, but he said he had left open the possibility of teaming with Nenad Zimonjic against the world's top team of Bob and Mike Bryan.
Serbian captain Bogdan Obradovic said he was yet to make a decision on the combination, however.