Danish teenager Holger Rune has accused Casper Ruud of shouting in his face after their French Open quarter-final on Wednesday night.
Rune also denied demanding his mother leave the stadium during the match.
Norwegian eighth seed Ruud won a tense encounter in four sets, 6-1 4-6 7-6 (2) 6-3, in a match completed shortly before 1am local time.
After Rune had questioned the line call when Ruud hit a winner on match point, the pair shared a frosty handshake at the net.
Later Rune told Danish newspaper Ekstra Bladet: “The team is really nice and sweet, but then he goes straight to me and shouts ‘Ja!’ straight up in my face.
“I thought ‘what the hell are you doing?’. You just do not do that. You can cheer as much as you want on the court, I do it myself when I win.
“But that’s just a lack of class. He should have had more respect.”
The claim was denied by Ruud’s father and coach Christian, who told Eurosport: “It is simply a lie from Holger.
“It is nothing more to talk about, because it is a pure lie. Our focus is now on the match on Friday.”
Rune also denied yelling at his mother to leave his players’ box.
The 19-year-old could be heard shouting ‘leave’ during the match, and mother Aneke did vacate her seat.
“First of all, I didn’t tell my mother to leave the stadium,” Rune told Eurosport. “That’s not why. It was another person. So that’s wrong.”
Ruud will face Croatian 20th seed Marin Cilic for a place in the Roland Garros final.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here