Jordan Thompson has given Australia the flawless start to the Davis Cup quarter-final against the U.S. in Brisbane with a four-set win.
The unheralded Thompson stunned world number 15 Jack Sock in four sets in the opening rubber before Kyrgios saw off the big-serving John Isner 7-5, 7-6 (7/5), 7-6 (7/5).
One win from the remaining three matches will deliver Australia, underdogs in pre-tie betting, a semi-final in September against either Belgium away or Italy in Australia.
It sparked jubilant celebrations at Brisbane's Pat Rafter Arena with captain Lleyton Hewitt and his teammates Jordan Thompson, Sam Groth and John Peers, whose behind-the-scenes support Kyrgios credited as been central to his recent rise.
10sBalls Top Stories In Case You Missed It The United States and Australia will be facing each other in the Davis Cup competition for the second time in as many years when they meet again during quarterfinal action this week.
Nick Kyrgios has sent Australia through to the Davis Cup semifinals, with an emphatic straight-sets win over American Sam Querrey.
In the decisive reverse singles on Sunday, Sock will face Kyrgios and Isner takes on Thompson.
"I've got a head cold right now and trying to fight through it - not feeling great".
"We knew it was going to be tough today", said Kyrgios. In that semifinal match, most of the crowd was in favor of Federer, the Australian Open champion who also won at Indian Wells before Miami.
Britain have slipped behind in their Davis Cup quarter-final against France, after Kyle Edmund was dispatched by Lucas Pouille in the first rubber at Rouen's Kindarena.
The International Tennis Federation will consider at its annual general meeting in August whether ties from next year will be reduced to best-of-three matches instead of five, and be played over two days instead of three.
American Jack Sock was in no mood to talk after his shock Davis Cup defeat to Jordan Thompson on Friday.
Querrey had beaten Kyrgios last month at the ATP event in Acapulco. "Playing for your country, there's no bigger honor in tennis".
He broke Querrey twice after the American led 4-1 as he attempted a comeback in the third set.
Hewitt said he felt there was no reason why his team couldn't be the first Australian side to win since 2003. "Those guys watch me play a lot when I'm at the Masters events or playing semi-finals or finals and I can set a good example if I beat a lot of these guys".