A lively clash saw Wayne Rooney's Rams take the lead in the 77th minute, but the Posh fought back superbly, with teenager Harrison Burrows equalising in the 91st minute, before Siriki Dembele sent the Peterborough fans into hysteria by scoring the winner in the tenth minute of stoppage time.
Speaking after the game, super-sub Burrows gave his insight into the dramatic win, and revealed: “The manager just sent me on to try and change the game.
“He told me to stay high and play more as a winger than a wing-back. He wanted me to try and make an impact by scoring or creating a goal.
“He told me to get in the game as quickly as I could and just play with confidence as I had nothing to lose. We work hard on getting wingbacks on the end of crosses and luckily I managed to do that and score.”
The local lad continued: “And we really felt we could go on and win the game. We rushed back to get started again and we dominated the final 10 minutes.
“I thought I was going to get on the end of another cross to score again, but a defender got in the way. Luckily the ball fell to Siriki who has the bit of magic required to score from that position.
Peterborough will look to carry their positive momentum into the midweek action, when they take on Cardiff City at home tomorrow evening.
We’ve gathered the best of today’s transfer speculation below…
1. Cherries still in hunt for Delap
Bournemouth are said to still be pursuing a loan move for Manchester City's starlet striker Liam Delap. The 18-year-old, who is also of interest to Preston and Millwall, made his senior debut for Pep Guardiola's side last season. (BBC Sport) Photo: Charlotte Tattersall
2. Bournemouth among favourites to sign Cahill
Bournemouth have been named second favourites to sign free agent defender Gary Cahill, behind Southampton. The ex-Chelsea man as released by Crystal Palace at the end of last season, and a number of sides are said to be keen on snapping him up. (SkyBet) Photo: JUSTIN TALLIS
3. Eagles join O'Brien hunt
Crystal Palace could be set to challenge Leeds United for Huddersfield Town's £7m-rated midfielder Lewis O'Brien. The Eagles, who lost their opening game of the season 3-0 to Chelsea, have already beaten the Whites to signing Blues midfielder Conor Gallagher on loan this summer. (Football League World) Photo: George Wood
4. Forest lodge defender bid
Nottingham Forest have made a £1.5m bid for Reading defender Tom Holmes, according to reports. It is suggested that the Royals could be forced into selling, due to a need to balance their books with sales. (Football Insider) Photo: Alex Burstow