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...
5. Baggies suffer blow in pursuit of ex-Hull star
West Brom are interested in signing Al-Ahli and ex-Hull City midfielder Mo Diame, however it has now been reported that the 34-year-old may struggle to gain a work permit thanks to the changing of rules following Brexit. (The Sun) | Getty Images
6. Ex-Preston favourite set for Sunderland exit
Former Preston North End loanee Aiden McGeady is reportedly set to depart Sunderland when his contract expires this summer. The winger enjoyed a brilliant spell at Deepdale during the 2016-17 season, scoring eight goals and assisting another nine for the Lilywhites. (The Sun) | Getty Images
7. Ex-Terriers owner could return
Ex-Huddersfield Town owner Dean Hoyle is reportedly in talks to rebuy the club following Phil Hodgkinson’s departure. Hoyle sold the club in 2019. (BBC) | Getty Images
8. Ex-Boro striker joins MLS
Watford striker Ashley Fletcher has joined New York Red Bulls on loan with an option to buy. The move comes just seven months after the 26-year-old left Middlesbrough on a free. (Watford FC) | Getty Images