Nick Kyrgios

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.

Federer: Kyrgios no chance of winning Australian Open

Federer, who has claimed four Australian Open titles himself, believes Kyrgios isn't experienced enough to go the full length.

"To win, he drops, in my humble opinion,'' Federer told Fairfax Media

''To do anything, yes, first week no problem, but to go all the way it's a long way, and he's never been into a semis before, so first he has to prove to the world and himself that he can make the semis.

"So for me to start talking about him winning the tournament, Lleyton [Hewitt] never did it, and he was two times world No.1 at the end of the year.

Wimbledon: Nick Kyrgios in heated row with journalist

The Australian 15th seed received a warning from umpire Jake Garner at the start of the third set after complaining about a decision and he completely lost his head before reaching the third round with a 6-7(3-7), 6-1, 2-6, 6-4, 6-4 victory.

Asked afterwards whether his antics were distracting for other players, Kyrgios lost his cool.

"What did I say to the umpire today?" he said.