Australian Open credentials

Nick Kyrgios, battling injury, loses his cool, smashes racket and hurls it into empty stand

Kyrgios was up to his usual tricks in a straight-sets defeat to Croatia's Borna Coric in a warm-up event at Melbourne Park on Friday, mixing some brilliant play with a mid-match dummy-spit.

The 25-year-old firebrand was warned by the chair umpire during the second set of his 6-3 6-4 defeat, after smashing a racket and hurling it into the largely empty grandstand.

He also vented his frustration over the blustery conditions on the outside court and ongoing pain in his troublesome knee, which he said flared up last year and has not fully settled.