Tiemoue Bakayoko contested Gennaro Gattuso's claim that it took the midfielder eight minutes to get ready when asked to warm up as a substitute during AC Milan's victory over Bologna, with the France international saying he prepared himself "immediately".
Gattuso and Bakayoko were seen exchanging cross words during the first half of Milan's 2-1 victory at San Siro on Monday, after which Gattuso said: "I told Bakayoko to warm up, but it took him eight minutes to get ready."
Jose Mauri was sent on for the injured Lucas Biglia in his stead, and the incident comes soon after Bakayoko, who is at Milan on a season-long loan from Chelsea, had to apologise to his team-mates after arriving an hour late for training.
Bakayoko countered Gattuso's assessment of the incident in a tweet, saying: "It has been several weeks since I was spoken about in the press but I decided to say nothing and continue to work.
"What happened tonight and the interpretation people are trying to give to it compel me to react immediately, because I do not accept that I should be considered a player who refuses to enter the field when his coach asks him and who does not respect his club and his team-mates.
"I was ready to give 200 per cent even if I had to play only five minutes tonight. When Lucas started to suffer on the ground, I was asked to prepare myself in case there was a change. So I prepared myself immediately and went to warm up for 2/3 minutes maximum.
"Then I was asked to return to the bench. That all happened I think between the 23rd minute and the 26th.
"It's when I sit on the bench that the coach speaks to me in unexpected terms and I only repeat his words. Nothing more.
"Let it be clear: I have never refused to come on to play and I do not get overheated. It seems to me that the images speak for themselves.
"I had only one desire, to enter the field and help my team-mates as I have always done and as I will do until the end of the season."
Milan sporting director Leonardo expressed sympathy for the midfielder, who last month was at the centre of a racism storm when Lazio fans allegedly directed monkey chants at Bakayoko and team-mate Franck Kessie.
"Bakayoko has been targeted too much," Leonardo told reporters.
"There have been too many things highlighted in public. It must not be nice to live what he is experiencing."