Nick Kyrgios has fired a broadside at Matthew Johns after the former NRL star criticised the tennis player's walkout in Shanghai on Tuesday.
Kyrgios retired early from his match against Steve Johnson in an apparent protest of the chair umpire.
The ATP fined the Australian Davis Cup player a total of almost $40,000 -- his prize money for the first-round appearance and a smaller sanction for unsportsmanlike conduct.
Numerous media personalities, including shock jock Alan Jones, took the opportunity to slam Kyrgios, but it was Johns' radio appearance that caught the player's eye.
“It’s just disgraceful behaviour," Johns said on Triple M.
"People pay good money to watch this match. He tells supporters courtside that if he loses the first set he’s going to walk off, does it, then tries to go and apologise on Twitter saying he’s got a tummy bug. Please."
Kyrgios also withdrew from a doubles match that was to be played on Wednesday, having said he was ill leading up to his controversial meeting with Johnson.
On Thursday, he fired back at Johns.
"Why is Matty Johns talking about individual sports? Didn't he like doing things in groups?" he wrote.
Johns was previously named as one of the Cronulla Sharks involved in a group sex scandal in 2002.
He is not the first Australian athlete to be on the end of a Kyrgios sledge on Twitter.
AFL players Taylor Walker and Patrick Dangerfield engaged the tennis star in a war of words two years ago.
Kyrgios responded: "I don't even know who Tex walker is lol."