Answering questions posed by readers of the Evening Chronicle, Pardew admitted he, owner Mike Ashley and managing director Derek Llambias, with the help of chief scout Graham Carr, should have recruited one more man to go straight into the first-team squad.
Pardew said: "Myself, Mike and Derek all agree we should have bought one more senior player in here. For whatever reason, it did not happen.
"We have learnt from that, and that is what comes from the luxury which is the security of the owner.
"The owner has great faith in my ability and I have to reward that with what I think when we make an error and say we have made a mistake.
"He accepts that and as a team we have to learn from it. Myself, Graham, Derek and Mike needed another player in and we did not get him.
"But it is not Graham's fault, Derek's fault or Mike's fault or mine - it is a collective thing and we have to take that all on the chin. We got that wrong."