took aim at tennis wonderkid Cruz Hewitt after the 16-year-old trained with world No. 1 ahead of the . The teenager is the son of 2001 US Open champion and 2002 Wimbledon winner Leyton Hewitt and is starting to make a name for himself in his own right.

Kyrgios hasn't featured in a Grand Slam since reaching the quarter-finals of the US Open in 2022 due to a host of injury problems.

But he will play at the Australian Open later this month after coming through a singles match and two doubles matches alongside Novak Djokovic at the Brisbane International.

Kyrgios is known for his outspoken views and hasn't been afraid to share his opinions in the past. And he appeared to be unhappy that Hewitt had practised alongside Sinner at the Rod Laver Arena.

Hewitt, who has been handed a wildcard to appear in the Australian Open qualifying draw, shared an update with his followers on Saturday as he posted a picture of himself standing beside Sinner following their practice session. And Kyrgios replied with an emoji of a syringe as he wrote: "Cooked post."

The 29-year-old returned to the platform a short time later as he posted a crying face emoji and penned: "Love ya Cruz but this is wild." And he added a series of broken heart emojis in a third post as he commented: "Thought we were boys."

The syringe emoji is believed to have been in reference to Sinner last year after the banned anabolic steroid Clostebol was found in his urine at the Indian Wells in March.

Sinner's team argued in his defence that the samples had been contaminated after he received a massage from his physiotherapist, who had cut his finger and treated it with an over-the-counter spray.

And a tribunal found that the Italian was 'not at fault or negligent' in relation to two failed tests.

Kyrgios has habitually since the failed tests came to light and wrote in a social media post in August: "Ridiculous - whether it was accidental or planned.

"You get tested twice with a banned (steroid) substance... you should be gone for 2 years. Your performance was enhanced. Massage cream..."

And after being asked during a social media Q&A session whether he would consider teaming up with Sinner for a doubles match, the Australian said: "I only play with CLEAN players."

Sinner, meanwhile, stated after being cleared of any wrongdoing: "I will continue to do everything I can to ensure I continue to comply with the ITIA's anti-doping programme and I have a team around me that are meticulous in their own compliance."