Milan's Spanish midfielder Suso laid into Lazio star Sergej Milinkovic-Savic after learning that the Serbian spat at him during their Coppa Italia semi-final last week.
Milinkovic-Savic was booked for a foul on Suso in extra-time of that match and appeared to spit at his opponent as he berated him for going down too easily.
Milinkovic-Savic was denied by Milan keeper Gianluigi Donnarumma in the subsequent penalty shoot-out as the Rossoneri won 5-4 to progress to the final against Juventus. Suso did not participate in the shoot-out, having been substituted with 12 minutes remaining.
Suso claims he did not realise that Milinkovic-Savic had spat at him until Donnarumma filled him in after the game.
"These are things that must never be done – I never do them – but everyone is different. And in any case we are in the final, not him."
(You may also be interested in 'He Should Leave': Super Agent Urges Italian Star to Quit AC Milan as Real Madrid Eye Potential Deal)
Milinkovic-Savic's performances this season have seen him linked with a move to Manchester United. He has scored 11 goals for Lazio, who currently occupy the fourth Champions League spot in Serie A.
The Biancocelesti lost 1-0 to Juventus on Saturday and could slip out of the top four if Inter beat their city rivals when their Milan derby clash is rearranged after being postponed following news of the death of Davide Astori.
The win against Lazio extended Milan's unbeaten run to 13 games, dating back to December. They are still eight points outside of the Champions League places though.