The U.S. Davis Cup team's path to the semifinals goes through world No. 1 Novak Djokovic now.
The loss by the Bryan brothers in Saturday's doubles match ensured that the U.S. can't beat Serbia without taking down its leader.
Sam Querrey, the highest-ranked American at No. 20, faces Djokovic at noon Sunday at Taco Bell Arena. If Querrey wins, No. 23 John Isner will face No. 44 Viktor Troicki to decide the tie.
Serbia leads 2-1.
"Sam is carrying confidence from his win (Friday)," U.S. captain Jim Courier said. "He just had a good practice. He knows he's going up against a great player. He has played him recently a couple times, and he's played him tough in those matches. We're not looking for a lot of surprises. It's going to come down to execution. Sam has every reason to feel confident.
"It's one of those matches where you go out and lay it on the line and hold your head up one way or the other."
Querrey is 1-5 against Djokovic in his career. The past four matches have been competitive, including a four-set loss for Querrey in the first round of the 2010 Davis Cup and a three-set win last fall in the Paris Masters.
Most recently, Djokovic beat Querrey 6-0, 7-6 (6) last month in Indian Wells, Calif.
Djokovic beat John Isner on Friday in straight sets. Isner was able to extend him to a tiebreaker in the first set and to 12 games in the third set, but couldn't match Djokovic's consistency.
"He's No. 1 in the world. You've got to play great to beat him," Querrey said. "If I'm going to win that one, everything is going to have to be working."
If Querrey wins - that would be less of a shock than what transpired Saturday - the pressure will shift to Isner.
Isner never has played in a fifth-and-decisive match in the Davis Cup. He's 1-3 in last-day matches, including five-set losses to Thomaz Bellucci of Brazil earlier this year and to Djokovic in 2010.
By the time he takes the court, he will have been waiting about 48 hours since playing the opening match of the tie.
"I've just got to do my best to stay positive," Isner said after Friday's loss.
Isner is 1-3 against Troicki, who like Isner has played some of his best tennis in Davis Cup competition.
"What he does best is his defensive play," Isner said. "He's not going to blow you off the court with a lot of winners, per se, but he retrieves a lot and makes you hit a lot of extra balls. So the game plan is the same for me. I've got to go out and keep playing big and believing in it and try to cut down on my errors. If it comes to me vs. him, I'll be excited and ready to go, that's for sure."
Troicki, who lost in five sets to Querrey, said he's hoping to play an exhibition match against Isner. If not, he's ready, too.
"I beat him last time in Davis Cup," Troicki said. "I have a positive score against him. So it won't be easy, but I feel confident playing against him."
Chadd Cripe: 377-6398, Twitter: @IDS_BroncoBeat