Filip Krajinovic received a very unusual code violation from the umpire for not wearing a mask to go to the toilet at the 2021 Australian Open.
While Daniil Medvedev had a furious bust-up with his coach, Krajinovic had his own stresses to contend with during their drama-filled third-round match.
The fourth seed Medvedev was forced to dig deep to battle past the 28-year-old on Saturday, but came through, 6-3 6-3 4-6 3-6 6-0.
The Russian forced his coach Gilles Cervara from the empty stands in Rod Laver Arena following several rants in his direction in a tempestuous feud, but perhaps the strangest incident was Krajinovic's code violation.
As the Serb left the court to go to the toilet, he neglected to put on his face mask, something for which he was immediately picked up on - quite rightly - by the umpire.
'I didn't know the rule!' - Maskless Krajinovic gets very unusual violation
Krajinovic ranted with his coaches in his chair after receiving the formal warning, before pleading that: "I didn't know the rule!"
Medvedev will next take on American Mackenzie McDonald in the last 16 at Melbourne Park.
'Let me play!' - Astonishing moment Medvedev tells his coach to leave stadium
In completing the heated victory, the 25-year-old extended his winning streak to 17 matches and reached the fourth round.
Russia could end up with an Open era record four men in the last 16 of a Grand Slam, with Medvedev leading the charge of his compatriots.
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