Posh fielded a much-weakened side and were defeated 2-0 by a motivated Cheltenham side who kept themselves alive in League One with victory.
Posh are now set to finish fourth in the table unless they record an unlikely thumping of Bolton on the final day.
RATINGS KEY: 10-Out of this world, 9-Brilliant, 8-Excellent, 7-Very Good, 6-Okay, 5-Poor, 4-Stinker
RATINGS KEY: 10-Out of this world, 9-Brilliant, 8-Excellent, 7-Very Good, 6-Okay, 5-Poor, 4-Stinker