He told the Milton Keynes citizen: "I have said it before and I'll have to say it again - if you keep making mistakes then eventually people are going to be replaced.
"They've all got to stand up and be counted. Not just the back four or five but all of them - all of those not doing their jobs.
"You have got to be ruthless and move forward and keep improving.
"I am not saying there are going to be massive changes but we want to start building, and conceding the amount of goals we do is not good enough. Either improve or be changed."