Watch: Nick Kyrgios serves underarm ace and deliberately hits ball at Rafael Nadal at Wimbledon

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The two have been locked in a war of words over the last few months, with Kyrgios trading insults with Nadal and his uncle Toni, and that threatened to spill out on to Centre Court in the Spaniard's 6-3 3-6 7-6 (5) 7-6 (3) victory.

There were the customary underarm serves and constant chatter with the umpire, but there was almost a flashpoint in the third set when Kyrgios thrashed a forehand straight at Nadal and opted not to apologise.