The junior tennis player who slapped his opponent in the face following a match earlier this week has issued an apology ... saying his actions were "wrong and completely out of line."
Just three days after 15-year-old Michael Kouame smacked 16-year-old Raphael Nii Ankrah following a loss at an ITF juniors tournament in Ghana ... he said he was very sorry.
Kouame -- who posted the mea culpa on his social media page -- said he acted out and slapped Ankrah after hearing heckling from the crowd during the match.
"I was repeatedly verbally abused by a large number of individuals in the crowd, including insults to my mother in particular," Kouame said.