Boris Becker has referred to Australian tennis star Nick Kyrgios as a "rat", after the latter criticised Alexander Zverev for partying during the coronavirus pandemic.
German player Zverev was seen dancing in a club on Sunday in a video posted online.
Kyrgios branded Zverev "selfish" as he had claimed he would be self-isolating after taking part in the controversial Adria Tour last week.
Several players have tested positive for Covid-19 in the wake of the tournament in Croatia, with Kyrgios taking to Instagram to say Zverev should have stayed true to his word by isolating.
— Boris Becker (@TheBorisBecker) June 30, 2020
"If you have the audacity to ... put out a tweet that you made your management write on your behalf saying you're going to self-isolate for 14-days and apologising to ... general public for putting their health at risk. At least have the audacity to stay inside for 14 days."
That's when six-time grand slam champion Becker decided to get involved, calling out Kyrgios for his criticism of Zverev.
"Don't like no #rats! Anybody telling off fellow sportsman/woman is no friend of mine! Look yourself in the mirror and think your (sic) better than us..."
Kyrgios responded by defending his right to call out world number seven Zverev.
"For goodness sake Boris, I’m not competing or trying to throw anyone under the bus. It’s a global pandemic and if someone is as idiotic as Alex to do what he has done, I’ll call him out for it. Simple."
@TheBorisBecker is a bigger doughnut than I thought. 😂😂 can hit a volley, obviously not the sharpest tool in the shed though.
— Nicholas Kyrgios (@NickKyrgios) June 30, 2020
Becker went on to say that "We should protect our families/loved ones and follow the guidelines but [I] still don’t like rats."
Kyrgios then referred to Becker as a "doughnut".
Becker also said he hopes Kyrgios can one day win a grand slam.
"I really would like to see @NickKyrgios fulfill his potential and win a grandslam! He would be an incredible role model for for the youth of the world addressing the issues of equality/race/heritage! Man up buddy and deliver!