City suffered a potentially fatal blow to their hopes of retaining their Barclays Premier League title as they were beaten 2-0 by their bogey side at Goodison Park.
Manager Roberto Mancini did not appear for post-match interviews, leaving first-team coach Platt to answer questions.
When asked why Mancini did not speak, Platt told Sky Sports: "He is a bit angry, as you can imagine.
"He is just taking stock of the situation and calming down. He doesn't want to come out here and say anything that might get him in trouble."
When asked what Mancini might be angry about, Platt said: "Everything in general, our performance - we weren't really at it throughout the game.
"We got outworked by Everton. When you do have moments when you can get back into it, it doesn't go for you."