And the goalkeeper has warned Darren Ferguson's side that a near full-strength Newcastle – who lead the Championship by two points – will be looking to avenge the loss at St James's Park tomorrow.
Boss Chris Hughton made wholesale changes for Sept
ember's third-round tie at London Road, handing a number of players their debuts, and his team's inexperience cost them as they lost 2-0.
With Tim Krul playing in goal that night, Harper did not travel, and he is "looking forward" to the opportunity to set the record straight at St James's Park in front of an expected 40,000-plus crowd.
"I wasn't at Peterborough, but I'm told that their players were milking it against a lot of our young lads, so we're looking forward to them coming up," Harper told the Gazette.
"I'm sure the fans will get behind us and show how tough a place St James's Park is to come."
Newcastle go into the game looking for a third successive win, having beaten Doncaster Rovers on their last home outing, and claimed a hard-fought 1-0 win at Sheffield United on Monday night.
Harper pulled off two superb injury-time saves at Bramall Lane, and despite Peterborough's lowly league placing – Ferguson's men are second from bottom – he is expecting another tough game before the latest international break.
Harper went on: "The Doncaster one was a big one – we went behind and won a tough, battling game. Those are the qualities you need in this league.
"It was proved again (at Sheffield United), and we're not underestimating Peterborough.
"We know that it'll be a tough game, and that they'll come and make it difficult for us, but it would be fantastic to take another three points."
The Sheffield United game was Hughton's first as permanent manager, and Harper has welcomed the end to months of uncertainty surrounding the ownership and managership of the club.
The 34-year-old added: "We're pleased it's all sorted. It's gone on and on – we've not known whether this or that was going to happen – but it's sorted now.
"The club's off the market, Chris Hughton's the manager, and hopefully we can get out of this division.
"Chris has done an incredible job in the circumstances, and fully deserves the appointment. All the lads are right behind him."
* Tickets are still on general sale for the game. Cash turnstiles at numbers 9,10,57,66,67 & 83 will be open from 1:30pm tomorrow.
