Mar 30, 2017; Miami, FL, USA; Nick Kyrgios of Australia (L) shakes hands with Alexander Zverev of Germany (R) after their match in a men's singles quarter-final during the 2017 Miami Open at Crandon Park Tennis Center. Kyrgios won 6-4, 6-7(9), 6-3. Mandatory Credit: Geoff Burke-USA TODAY Sports
Mar 30, 2017; Miami, FL, USA; Alexander Zverev of Germany slams a ball in frustration after losing a game against Nick Kyrgios of Australia (not pictured) in a men's singles quarter-final during the 2017 Miami Open at Crandon Park Tennis Center. Kyrgios won 6-4, 6-7(9), 6-3. Mandatory Credit: Geoff Burke-USA TODAY Sports
Mar 30, 2017; Miami, FL, USA; Alexander Zverev of Germany argues with the chair umpire during a changeover against Nick Kyrgios of Australia (not pictured) in a men's singles quarter-final during the 2017 Miami Open at Crandon Park Tennis Center. Kyrgios won 6-4, 6-7(9), 6-3. Mandatory Credit: Geoff Burke-USA TODAY Sports
Mar 28, 2017; Miami, FL, USA; Nick Kyrgios of Australia argues with the chair umpire in a match against David Goffin of Belgium (not pictured) on day eight of the 2017 Miami Open at Crandon Park Tennis Center. Kyrgios won 7-6(5), 6-3. Mandatory Credit: Geoff Burke-USA TODAY Sports
Mar 30, 2017; Miami, FL, USA; Alexander Zverev of Germany reacts after missing a shot against Nick Kyrgios of Australia (not pictured) in a men's singles quarter-final during the 2017 Miami Open at Crandon Park Tennis Center. Kyrgios won 6-4, 6-7(9), 6-3. Mandatory Credit: Geoff Burke-USA TODAY Sports
Mar 30, 2017; Miami, FL, USA; Nick Kyrgios of Australia serves against Alexander Zverev of Germany (not pictured) in a men's singles quarter-final during the 2017 Miami Open at Crandon Park Tennis Center. Kyrgios won 6-4, 6-7(9), 6-3. Mandatory Credit: Geoff Burke-USA TODAY Sports
Mar 30, 2017; Miami, FL, USA; Alexander Zverev of Germany reacts towards his player's box after wining the second set against Nick Kyrgios of Australia (not pictured) in a men's singles quarter-final during the 2017 Miami Open at Crandon Park Tennis Center. Kyrgios won 6-4, 6-7(9), 6-3. Mandatory Credit: Geoff Burke-USA TODAY Sports
Mar 30, 2017; Miami, FL, USA; Nick Kyrgios of Australia argues a call against Alexander Zverev of Germany (not pictured) in a men's singles quarter-final during the 2017 Miami Open at Crandon Park Tennis Center. Kyrgios won 6-4, 6-7(9), 6-3. Mandatory Credit: Geoff Burke-USA TODAY Sports
Mar 30, 2017; Miami, FL, USA; Alexander Zverev of Germany hits a backhand against Nick Kyrgios of Australia (not pictured) in a men's singles quarter-final during the 2017 Miami Open at Crandon Park Tennis Center. Kyrgios won 6-4, 6-7(9), 6-3. Mandatory Credit: Geoff Burke-USA TODAY Sports
Mar 30, 2017; Miami, FL, USA; Nick Kyrgios of Australia reacts after winning a point against Alexander Zverev of Germany (not pictured) in a men's singles quarter-final during the 2017 Miami Open at Crandon Park Tennis Center. Kyrgios won 6-4, 6-7(9), 6-3. Mandatory Credit: Geoff Burke-USA TODAY Sports
Tempers flared between Nick Kyrgios and Alexander Zverev late in their Miami Open quarter-final on Thursday when a botched line call and contentious decision by the chair umpire to allow a challenge on the point caused both players to react angrily.
The pivotal moment of the Australian's 6-4 6-7(9) 6-3 triumph came on the first point of the sixth game in the deciding set, when a lob from Germany's Zverev sailed long.
The linesman mistakenly called the ball in and Kyrgios, despite believing it was out, decided to try a low percentage 'tweener' shot between his legs before challenging.
Chair umpire Fergus Murphy allowed the challenge, a decision that former player Brad Gilbert called "wrong" during television coverage, and replays showed the ball was indeed out.
The point was awarded to Kyrgios, which left Zverev seething, the German arguing that the 12th seed should not have been allowed to challenge the call after hitting the ball.
Flustered, he lost the game, which turned out to be the only service break of the set, and Zverev gave Murphy a piece of his mind at the next change over.
"You might cost me the match," he said. "You know that. The decision is absolute crap."
Kyrgios, meanwhile, was not happy either, giving the linesman a verbal spray for missing the call in the first place, but settled down to hold serve and finally clinch victory on his sixth match point, earning a semi-final against Roger Federer.
(Reporting by Andrew Both in Cary, North Carolina; Editing by John O'Brien)