LOS ANGELES (AFP) - Australia's Nick Kyrgios dethroned John Isner by beating the three-time defending champion 7-6 (7-3), 7-6 (7-4) in the Atlanta Open tennis final to win his second ATP Tour crown.

The second-seeded Kyrgios needed one hour and 47 minutes to win his first career match over Isner and snap the hard-serving American's 15-match winning streak.

"Returning is very crucial against John," said Kyrgios. "That serve is world class."

The 21-year-old Kyrgios also improved to 2-1 in ATP Tour finals. His only other title came in February at the Marseille indoor tournament.

Kyrgios, of Canberra, had his back against the wall on Sunday in his opening service game when he faced three break points. He saved them all and then won five straight points to hold serve.

Kyrgios will rise to a career high ranking of 16 with this win. He lost to Isner at ATP Tour tournaments in Madrid and Montreal last year.

Isner was seeking to become just the fifth active player to win four consecutive titles, which would have allowed him to join Novak Djokovic, Rafael Nadal, Roger Federer and Kei Nishikori.

He has appeared in the Atlanta final in six of the tournament's seven years, also finishing runner-up to Mardy Fish in both 2010 and 2011.