The Gills boss said, "We didn't perform tonight and it wasn't acceptable as far as I'm concerned - especially in the first half.
'I have protected my players since I have been doing this job but I can't protect them tonight after that performance - it just wasn't good enough."
'No disrespect to Northampton but I expected those 11 players out there tonight to put on a better performance in the first half and win this game.
'So forget about how many changes we made because we should have won the game. But we didn't because we didn't perform. Some of the players didn't deserve to wear the shirt in the first half.
'We haven't had many bad times here and I think that's the first time we have gone out of this Cup in the first round in quite a few years.
'There was no desire and it's hard for me to say that, because that's what this club is all about.'
The Gills left the pitch at the end of both halves to boos and jeers – and Hessenthaler felt the criticism of his team by the fans was justified:
'I apologise to the fans on behalf of my players because they didn't deserve that. They pay good money to come and watch Gillingham. If the players are not going to perform they must at least work hard.
'They've had it in the earhole and I've told them I'm not putting up with it because I'm not having a season like I had last year, and if players don't want to play for me then they can go elsewhere.
'It's up to the players now. They will be in early tomorrow when they thought they would be off and we'll get it right. If it means we have to be in every day nine-to-five until we get it right then we will be.
'We are going into a big game on Friday night and I'm sure the fans will be looking for a response. The pressure is on us now because we have got to perform and we have got to win.'