Their Championship clash against Hull City was a must-win, however Posh were beaten 3-0 by their fellow relegation rivals.
The defeat leaves them glued to the bottom of the table - eight points from safety and with a game in hand over 21st place Reading.
Peterborough will now host Premier League champions Manchester City in the FA Cup Fifth Round tonight.
The two sides have only ever met once previously - another cup tie in February 198 - where the visitors came out 1-0 winners at London Road Stadium.
Peterborough United will then face another tough test in Huddersfield Town in the Championship on Friday evening.
The Terriers currently sit third in the league and are vying for an automatic promotion spot.
Here are the best of today’s transfer rumours...
1. QPR sign ex-Arsenal youngster
QPR have confirmed the signing of free agent Stan Flaherty. The 20-year-old midfielder has been without a club since his departure from Newcastle United. (Football League World) | Getty Images
2. Fulham linked with ex-Liverpool striker
Fulham are reportedly eyeing a move for former Liverpool and Manchester City striker Mario Balotelli. The 31-year-old has scored 10 league goals with Turkish club Adana Demirsport this season. (The 72) | Getty Images
3. Tottenham join race for Robins prospect
Tottenham Hotspur are the latest Premier League club to join the race to sign Bristol City’s Alex Scott. West Ham, Leicester and Everton are also interested. (LondonWorld) | Getty Images
4. Posh striker makes non-league switch
Peterborough United’s Harmeed Ishola has joined Maldon & Tiptree on loan. The striker joined Posh last summer. | Getty Images