Steve Davis gives his post match reaction from the Alexandra Stadium.
He added: "Hopefully we can add to the group next week to give us a boost and we will pick up on that next week."
"That is the poorest we have been as a group and I didn't need to tell them that the commitment we have shown wasn't there today. We let a lot of people down today with that performance.
"We weren't switched on at the beginning of both halves and I share the frustration of the supporters because I expect better than that. We fell well below what I expect and no-one played well for us. Passing was loose and the quality wasn't there. We didn't work hard enough and that's the first time I've said to them that I thought that they had given up today. You got to show some fight and roll your sleeves up and we didn't do that and it could have been more.
"Every game this season we have been in it, up to a point but we weren't today and that is the most disappointing thing. We have been in close games and maybe lost by the odd goal or 2-0 but today was very one sided for too long. At 1-0 at half-time we were in with a chance but then it went away from us very quickly and there was no coming back from that from our point of view.
"In the end they always looked dangerous every time they went forward. They were good and no disrespect to them but we were really poor today, especially in that second half. Peterborough have been winning games and they are footballers with confidence and they played with that confidence today.
"At times in the second half we were just following people around and couldn't stop them, or find a way of doing it even though we had set up to do that and had worked on it. We made too many mistake and none of them played to their potential.
"We started the game poorly and they scored in that period. After that I thought we played some decent football at times in that first half and had some chances but we started the second half slow again and and bang, bang, bang before we knew it is 3-0 and then 4-0. It is extremely hard after that and I was disappointed with all aspects of our play after that. In possession, out of possession, defensively and I expect better than that. I want people to run about, close people down and do that ugly side of the game and we are not doing it enough.
After the defeat, Davis told the club's official web-site: "It was a horrible afternoon for everyone and there were not any positives to take from the game, aside from possibly Ryan Colclough's goal because it was a terrific strike but it was a mere consolation in the end.
Steve Davis described the 5-1 home defeat by Peterborough as 'a horrible afternoon' and was annoyed that his players did not show nearly enough fight in the second half as the result slipped away from us. The Alex boss was annoyed with the way we started both halves and our visitors from Peterborough were absolutely clinical on the counter-attack, scoring in the opening ten minutes and then adding two goals in the opening three minutes of the second half.