The Serb was unimpressed by Keane's comments about the manner of his departure from United this summer.
“I have respect for what he has done but he needs to understand that football has changed," Matic told The Times. “If I played for Chelsea, I cannot say I hate them. I cannot be angry when I'm talking to the press after the game.
“The way he behaved on pitch, 70 per cent of it is a red card today. You cannot throw a punch when all the cameras in the world are there. The real hero is when you go out on the street and say something, but he was always very nice with me, so what he says in public, to be honest, I don't really care. I know what I've done in my career and I'm very happy."
Matic is not the only United player to receive public criticism from former players and fans, with club captain Maguire a regular target for abuse.
The former Chelsea midfielder also condemned the treatment of the England international and slammed those who hide behind the safety net of social media to dish out abuse.
He added: “What people are doing to him, it is a disaster. Everything has to have limits and some of these people writing on social media, they don't have their own lives so they just have to write bad things about someone else."