BRISBANE, Australia (AP) Nick Kyrgios finished off John Isner with his 20th ace to give Australia a 2-0 lead over the United States in their Davis Cup quarterfinal on Friday.
Kyrgios won 7-5, 7-6 (5), 7-6 (5) after Jordan Thompson upset Jack Sock 6-3, 3-6, 7-6 (4), 6-4 on a hard court at Pat Rafter Arena.
Australia can clinch the tie and advance to a semifinal in September against Italy or Belgium with a win on Saturday in doubles. Sam Groth and John Peers are scheduled to play the American pair of Sam Querrey and Steve Johnson.
''Hopefully we can close it out tomorrow, it's been an unbelievable day,'' Kyrgios said.
''He's one of the best servers in the world, a proven player. I've been putting my head down and I returned really well.''
Isner said he ran into an in-form player.
''I felt like I played well enough to beat anyone out there, but not Nick,'' Isner said. ''He came up clutch.''
Kyrgios came from a break down in the first set, broke Isner to love in the 11th game, and clinched the set on an ace. In the second, Isner saved two break points at 5-5 and Kyrgios won the last three points. In the third, Isner saved a match point serving at 5-6 and lost the last three points again.
The 79th-ranked Thompson won both of his singles in his Davis Cup debut against the Czech Republic in February, but he was more impressive against No. 15 Sock, the highest-ranked player in the quarterfinal.
Sock looked out of sorts at times and served two double faults to hand Thompson his first break at 5-3.
The American rallied to win the second set, then recovered from 4-1 down to level the third set before Thompson won it in a tiebreaker. Thompson clinched the match in the fourth set by breaking Sock's service twice.
''I just tried to wear him down, and I thought I was fit enough to do that,'' Thompson said. ''I was not trying to go too big, that's not within my game.''