Feds' Posh reaction
Royals stopper Adam Federici was quick to apologise on his teammates' behalf to the fans who made the journey to London Road tonight.
"To come and support us here at Peterborough on a Tuesday night is a great effort, and I can only apologise on everyone's behalf.
"Thank you for coming down and giving us such great support tonight. All I can say is, as players, we are all so disappointed in ourselves and now all we can do is look to put it right at the weekend for you all."
Tonight, Peterborough were ruthless and Federici made a series of good saves to prevent the high-flying Posh outfit adding further to the scoreline at times.
"You've got to give full credit to Peterborough, they are a very, very good team for League One and every time we come here they give us a tough game, and they're on fire at the moment.
"But we didn't get going from the start. They played really good football and we didn't play good football at all.
"They didn't let us get out of our own half and they finished really well. As you can tell by the scoreline, they very much deserved to go through.
"They showed us how to win a cup game tonight, gave us a lesson definitely. It is just very disappointing on our behalf.
"The best way to get over this is to have another game very quickly, and we've got that in Yeovil on Saturday.
"It's another tough place to go, but I'm sure there will be a few changes to the first team and rightly so after our performance today."