Johnson felt he should shoulder the blame for the defeat as he made only one change from the 3-0 win over Coventry City at the weekend.
"Maybe I made the mistake of playing the same team after they put in all the effort on Saturday. We certainly didn't look like we had out legs today and I'll take the responsibility for that.
"I though we could go into the game on the back of a great result and play the same but it didn't work like that. We'll have a look at everything."