His best stretch of tennis came near the end of the second set. He trailed Alves 5-4 and had to fight off a pair of set points. Both times he responded with aces before eventually pulling even at 5-5.
In the tiebreaker, Alves jumped out to a 3-1 lead, but Isner won the next four points before closing out the set with successive aces.
He broke Alves in the fourth game of the third set to take a 4-2 lead and held on his final two service games, closing out the match by winning four consecutive points in the ninth game.
Querrey was impressive in his straight-set win over Brazil's top-rated player. He didn't finish with as many aces as Isner, but dominated all 15 of the games he served. He won 45 of the 47 first-serve points that went in and never faced a service break on his serve, winning all but 12 points on his serve in the three sets.
Querrey said he couldn't recall the last time he served as well.
"There's probably been a few, but not many," he said. "The court really helps my serve. When it hits, it really skids away. I mean I couldn't have served much better out there."
Querrey broke Bellucci in the eighth game of the first set and after holding his serve to close out the set, jumped to an early lead in the second set with a break in the first game. Both players then held serve the rest of the set, resulting in a 6-4 win for Querrey.
Querrey matched that feat in the final set, breaking Bellucci in the first game and then holding his serve the rest of the match. He clinched the victory when Bellucci hit a weak backhand into the net at match point.
The wins left team captain Jim Courier happy with his team's position in the best-of-five matchup.
"We're certainly pleased to be in this position," Courier said. "We have a lot of confidence in Bob and Mike. They're going to go out and lay it on the line. It will take a really special effort to beat them."