BRISBANE, Australia - A much-happier Nick Kyrgios sent Australia into the Davis Cup semifinals when he beat American Sam Querrey in the first of the reverse singles in Brisbane on Sunday.

Kyrgios' 7-6 (4), 6-3, 6-4 win gave the Australians an unassailable 3-1 lead over the US before John Isner won the dead rubber against Sam Groth 7-6 (5), 6-3.

The controversial Kyrgios, whose on-court behavior has led to a barrage of criticism from fellow players, commentators and fans, was the model of decorum and dedication in his two matches.

The 21-year-old revealed later that Australia captain Lleyton Hewitt had asked him to be the team's leader, and he was happy to accept the challenge.

Kyrgios, who once confessed to not enjoying tennis, said he was in a much better place nowadays and his recent results reflected his mindset.

"I'm playing better, but I'm just in a happier place," he said. "I'm going out and playing the game how it's meant to be played.

"I haven't been going back to the hotel hating the game or just trying to get through every day.

"I'm trying to get better every day, and that's a massive difference."

Kyrgios pushed eventual champion Roger Federer to the brink in the semifinals in Miami last week and has made the final four in three of his last four tournaments.

He said that during this run of good form he always had one eye on the Davis Cup.

"I've been looking forward to this tie for a long time now," he said.

"I always had one eye on it. When I was in the States I always knew I had to come here and play two big matches.

"It's a bit (of) a relief. It's one thing to say I've been preparing for it but to actually deliver, it feels pretty good.

"Obviously the way I've been playing for the past two months has created an expectation these couple of days," he added.

"It was a lot of relief to get through."

Australia will play either Belgium away or Italy at home in September's semifinals.

Belgium leads Italy 2-1 in its quarterfinal in Charleroi.

The other semifinal will pit Serbia against France, after they enjoyed victories over Spain and Britain respectively over the weekend.

Agence France-Presse