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Nick Kyrgios' opponents can only guess which second serve he'll deliver.

Kyrgios Keeps 'Em Guessing

Infosys ATP Beyond The Numbers explains how the Aussie keeps his opponents guessing

There is unpredictable, and then there is Nick Kyrgios.

The enigmatic 21-year-old Australian is a master of the mysterious when hitting second serves, keeping opponents off balance with his massive range of speed and spin. Sometimes it's an 83 mph kicking mule that deceptively comes at you slow, but then leaps off the court up over your head. Other times it's a 129 mph fastball that whizzes right by you for an ace. It's unreadable, often unhittable and unrelenting in the clutch.

Kyrgios takes the standard guidelines for hitting second serves on board, and then proceeds to throw them out the window. He is not the first player to have such a prolific mix of second-serve deliveries, but he is certainly one of the best at executing it on the biggest stages in the most important moments.

The ATP Stats LEADERBOARDS, powered by the Infosys Information Platform, identifies that Kyrgios has the third best Serve Rating on the ATP World Tour during the past 52 weeks against Top 10 opponents, with a 288.7 rating. The 6'4" (193cm) Aussie is sixth best on tour in the past 52 weeks against all opponents with second-serve points won, at 55.4 per cent. The mix is the primary reason. He gives you the kitchen sink with his second serve.

Kyrgios recently scored back-to-back wins against World No. 2 Novak Djokovic at the Abierto Mexicano Telcel in Acalpulco and at the BNP Paribas Open in Indian Wells. Kyrgios' second serve was simply spectacular.

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He won an impressive 62 per cent (29/47) of his second-serve points combined in both matches against one of the best returners in the game. Kyrgios' serve was not broken in either match, and he faced only one break point in 23 service games.

Second-Serve Points Won Against Novak Djokovic

• Acapulco 75% (15/20)

Indian Wells 52% (14/27)

In their Indian Wells round of 16 clash, Kyrgios had a substantial 46 mph difference between his slowest second serve and his fastest. To make things even more mind blowing, the two extremes happened one after the other late in the second set, helping him seal the match.

With Kyrgios serving at 5-6, 40/30 in the second set, he hit an 83 mph change-up out wide in the ad court that Djokovic barely made contact with above his head with his reaching backhand return.

Kyrgios' next second serve came at 3/2 in the tie-break – a blistering 126 mph ace right down the middle. Djokovic split-step to cover that direction, but the slicing, snarling delivery was still well outside his reach.

Djokovic's first-serve average speed for the match was 115 mph. Kyrgios hit 11 second serves that were faster than that. Djokovic's fastest first serve was 128 mph. Kyrgios hit one second serve faster – a 129 mph bomb down the middle of the ad court at 1-2, 40/0 in the second set.

Kyrgios' second serve did yield four double faults, but it also notched up three of his 14 aces. Kyrgios was lights out in this area during their Acapulco match, hitting 25 aces, while yielding just one double fault.

Kyrgios is not simply bending the traditional second-serve rules of our game. He is breaking them in half.