Speaking to the club website after the game, Coleman said: "I never really saw that performance coming. After 25 minutes in the first half I've got to hold my hands up and say I don't know what we were thinking or doing. But there were some bad individual errors.
"I was unacceptable and I need to apologise to the supporters for the performance. I don't know where it came from.
"We played ever so well against Palace on Tuesday night when we should have won the game and we went about our business in the right way. Then today we saw a complete reversal of that.
"It's something we need to sit down and talk about. We have another game on Monday so it will be interesting to see what performance we give then.
"We are looking at six first team players out and we have lost Aron Gunnarsson after 25 minutes - but that's not the reason we lost 4-0. "We lost 4-0 because too many people didn't do their jobs."
Copy righted photos from the game can be seen by clicking on http://www.coventrycity-mad.co.uk/ and then going on the photo gallery link.