Canada's Denis Shapovalov has apologised after shouting an obscenity at the crowd during a dispute with chair umpire Richard Haigh during his 7-6 (7/5), 3-6, 6-3 victory over Lorenzo Sonego.
A line call angered Shapovalov, who was then hit with a game penalty after he hopped the net to point at the mark on the Foro Italico clay.
The Rome fans did not appreciate Shapovalov's attitude and he was jeered while arguing with officials which saw him lash out at the crowd.
Shapovalov throws a tantrum
Chair umpire Haigh said: "I understand it was a kick serve, that's the mark I had but I didn't think it was that short. Denis, listen, because you crossed the net you're going to get another code violation. You can't cross the net."
Shapovalov replied: "No way! Come on I was just showing you the mark. Call the supervisor that's b*******! That's so unfair.
"I'm not doing anything unsportsmanlike. How can you give me a point penalty for that?" he further remonstrated.
Shapovalov apologised to the umpire and later acknowledged he was wrong to cross the net.
"It was the heat of the moment so I got emotional. I apologised after. Obviously it was my mistake. There's nothing they can do," Shapovalov said in his post-match press conference.
"I'll know the rule for next time. I definitely won't step over the net."
Bad behaviour in tennis has been under the spotlight thanks to Alexander Zverev's Acapulco outburst, and several severe instances of racket abuse.
The flame still burns
Meanwhile, former French Open champion Stan Wawrinka said he has recaptured his fire after he eliminated 14th seed Reilly Opelka 3-6, 7-5, 6-2 in their first round clash.
The win was Wawrinka's first on tour since last year's Australian Open.
"After two surgeries, at my age, I could easily stop playing because my career is way better than what I expected when I grew up, when I was young," Wawrinka said on Monday.
"But I still have this fire on me. I still believe that I can play great tennis. I still believe that I make some big results, maybe not now, but in few months."
Fognini keeps Italian flag flying
In a late match, home favourite Fabio Fognini overcame Austria's Dominic Thiem 6-4, 7-6(5).
"Of course I'm happy because I won," The Italian veteran said.
"It's never easy playing against a great champion. Happy to be here and another chance to play in this great atmosphere.
"It's always difficult, especially because now I'm 35," said Fognini.
"Physically, I'm quite OK. I feel good when I run. Of course I need to do some things on my game, try to push the ball harder because conditions are really slow. But these kinds of conditions are tough for everybody."