Alexander Zverev seals Germany's Davis Cup victory over Australia

Australia have lost their Davis Cup first-round tie in Brisbane after Nick Kyrgios was thrashed in straight sets by world No.5 Alex Zverev, giving Germany an unbeatable 3-1 lead.

The World No.14 looked frustrated from the outset on Sunday and required a second set medical time-out for his right arm before succumbing 6-2 7-6 (7-3) 6-2 at Pat Rafter Arena.

Australia have now been relegated to September's World Group play-offs while Germany move through to April's quarter-finals.

The final reverse singles rubber set to feature Australian No.2 Alex de Minaur against Jan-Lennard Struff was abandoned after Germany sealed the win.

Australia had to win both reverse singles rubbers on Sunday to claim the tie after doubles pairing John Peers and Matthew Ebden lost in five sets to Struff and Tim Puetz on Saturday.

Zverev stood tall on Sunday to ensure Germany won through to the quarter-finals for the first time since 2014.

The stage had been set for an epic clash between rising stars Kyrgios and Zverev.

And while Kyrgios started with an ace and cruised through his first service game, he looked out of sorts against the German and never found his rhythm.

Kyrgios appeared to be struggling with a right elbow ailment, taking a time-out for treatment while leading 4-3 in the second set.

Kyrgios was clearly restricted by the second set tiebreak, earning a point penalty to trail 4-0 after slamming his racquet into the ground following another unforced error.

Kyrgios made 34 unforced errors against the big-serving Zverev, who made him pay.

The German's serve again proving the difference: he slammed 15 aces and enjoyed a 71 per cent first serve percentage.

What was supposed to be the rubber of the tie became one way traffic after Zverev blew away Kyrgios to take the first set in 23 minutes.

Kyrgios tried to hang in but all but sabotaged his second set tiebreak with his racquet abuse penalty.

Zverev made short work of Kyrgios in the third set to secure a win and improve his head-to-head record to 5-2 against the Australian No.1 in all competitions.

Kyrgios - who had won six of his past seven rubbers - now has a 9-6 Cup singles record while Zverev improved his tally to 3-4.

The loss was a blow for the hosts, who qualified for last year's semi-finals and had won their past three home ties.

Germany will play either Great Britain or Spain in the quarter-finals.