Holders Swansea were dumped out of the Johnstone’s Paint Trophy after a 1-0 defeat to Peterborough at a deserted London Road.
A third-minute howler from giant Swansea defender Dennis Lawrence sparked their downfall at the hands of the League Two side.
Lawrence’s weak header back to goalkeeper Willy Gueret was seized upon by striker Danny Crow, who slotted his third goal of the season into the empty net.
And that proved to be the only goal as Posh claimed revenge for a quarter-final defeat at the hands of the Welshmen in this competition last season.
Midfield pair Richard Butcher and Shane Huke both came close to adding to the tally when forcing Gueret into spectacular saves with long-range drives.
Swansea striker Chris Jones was denied a debut goal by Posh stopper Mark Tyler and the visitors came even closer with Owain Tudor-Jones’ mis-hit volley which cannoned back off the crossbar.