"I felt like I played well enough to beat anyone out there, but not Nick," Isner said. "He came up clutch."
Davis Cup: Australia leads US 2-0 in quarterfinal →
"In my opinion I think he's a lot more mature now," Isner said of Kyrgios. "Right now, a lot of people could argue he's playing maybe the best tennis he's ever played."
Davis Cup: American Sock to play Aussie Thompson to open QF →