Darren Ferguson' s side matched their opponents on the possession front, but were unable to cope with a masterclass from opposition forward Fred Onyedinma, who set up two goals and scored one in a dazzling debut performance.
Speaking after the game, Posh boss Darren Ferguson said: “They started the game strongly, but we saw that through and got a bit of control in the game. We just needed to play with a little bit more belief.
“The reason we lost the game today was poor decision-making and a lack of concentration. We made it difficult for ourselves. You can’t give goals like that away in the second half.
“It’s nothing to do with the level, but the decisions we made. Even the first goal. We’ve got to stop the cross. It’s a foul though, he’s got both hands on my centre half, but sometimes you get and the sometimes you don’t.
“For the second, Frankie Kent made a terrible mistake and we were punished and three minutes later they put a cross in the box and the boy’s got no-one near him, the wing back hasn’t dealt with it and it’s an easy two goals.
“Then at that point you’re thinking this could be four or five, but it was never that sort of game.”
Next up, the Posh will look to bounce back tomorrow evening, when they take on Plymouth Argyle at London Road.
We’ve gathered the best of today’s transfer speculation below…
1. Hull winger set for exit
Hull City winger Thomas Mayer looks set to leave the club, last than a year after joining them. The Austrian made just six league appearances last season, and appears to be deemed surplus requirements at the MKM Stadium. (Hull Daily Mail)
Photo: George Wood
2. Palmer switch could boost Blackpool
Blackpool's hopes of landing Nottingham Forest man Jordan Gabriel look to have been boosted, following news that Forest are after Sheffield Wednesday's Liam Palmer. Gabriel played a key role in the Tangerines' promotion last season with an impressive loan spell. (The Sun)
Photo: George Wood
3. Morrell set for Pompey switch
Luton Town midfielder Joe Morrell is closing in on a move to League One side Portsmouth, according to sources close to the club. The Wales international made just seven league appearances for the Hatters last season, after joining from Bristol City. (The News)
Photo: Mike Hewitt
4. Swans to keep spending
Swansea City look set to spend some money in the transfer window, with chief executive Julian Winter insisting the club' owners will invest more into the club this season. The Swans signed Jamie Paterson, their first new signing of the window, last Friday. (BBC Sport)
Photo: Alex Burstow