Stefanos Tsitsipas hurt his own father in a mid-match meltdown during his clash with Australia's Nick Kyrgios at the ATP Cup.
Greek captain Apostolos Tsitsipas, who coaches the 21-year-old, was caught by Tsitsipas' angry racket swipe as he reacted to losing the opening set on a tie-break in Brisbane.
Tsitsipas Sr reacted with shock and moved to sit further away from his son, with a bruise visible on his arm.
Tsitsipas was given a warning by the umpire as well as a talking-to from his mother, Julia Apostoli.
At his post-match press conference, Tsitsipas said he was planning to speak to his father, saying: "It happened accidentally.
"I didn't mean to do it and straight away forgot about it and moved on from there. It happens. I wasn't aiming to do that. It's just it went out of control, unfortunately.
"Maybe I'll stay in my room for three days, grounded by my father."
The world No 6 then received a point penalty for hitting a ball in anger early in the second set and, although he levelled the match, it was Kyrgios, for once a picture of control down the other end, who eventually prevailed 7-6 (9-7) 6-7 (3-7) 7-6 (7-5).
The Australian fell on his back after a final backhand winner down the line as the home nation, who were already through to the quarter-finals, maintained their perfect record.
In the last eight, Australia will face Great Britain, who had a helping hand from Belgium in winning Group C.
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