Battling Posh undone by late strike from Jack Diamond as Stockport prevent Darren Ferguson's men taking all three points.
They say diamonds are forever and this particular Diamond went all the way for Stockport County as the visitors grabbed a stoppage time equaliser to prevent Peterborough United from following up the Wembley win against Birmingham City with three points against another side chasing promotion.
Ricky-Jade Jones had given Posh the lead, racing from the half-way line before coolly slotting past the goalkeeper, but it was a stop-start encounter at the Weston Homes Stadium, punctuated by serious injuries to Archie Collins and Cian Hayes with very few clear-cut opportunities in front of goal.
Collins suffered a knee injury with Ferguson describing the wound in the post-match press conference as 'deep' with the 'bone in view'.
That long stoppage for treatment meant there were 11 minutes added time in the first period, but Posh were good inside that first 45 minutes and could have had at least one penalty kick, but referee Charles Breakspear waved away the protests.
Addai in the County goal denied Jones in that first period while Jed Steer was largely untroubled in the Posh goal.
The JONES goal was one of the few times that Posh got it right in transition, Mothersille adding to his assists with a clever pass and the Posh number 17 nipped in front of the defender on the half-way line before racing clear to score his 17th goal of the campaign.
Stockport started the second half well without carving any clear-cut chances of their own with a James Norwood free-kick that went over and two fairly routine saves from Steer to keep out Oloafe and substitute Fevrier.
Posh had several chances in transition to add a second, but only a Jones shot that went wide and a number of Mills deliveries that failed to get a touch caused issues.
It was DIAMOND who had the last laugh as he drilled a left-footed effort from 20-yards into the bottom corner after Posh failed to adequately clear their lines.
Mills did have a chance to repeat his free-kick heroics deep in stoppage time, but he fired a free-kick over the crossbar.
Posh: Steer, Collins (sub De Havilland 14min), Wallin, Mothersille (sub Hayes 59min, sub, sub Lindgren 69min), Odoh, Poku, Jones, Kyprianou, Dornelly (sub Johnston 69min), Mills, Fernandez. Unused subs: Bilokapic, Nevett, Conn-Clarke.
Stockport County: Addai, Touray (sub Moxon 84min), Horsfall (sub Mingi 46min), Diamond, Olaofe (sub Andresson 74min), Collar, Pye, Wootton, Norwood, Bailey (sub Fevrier 46min) Hills. Unused subs: Wogan, Connolly, Cosgrove.
Half-time: Peterborough United 1-0 Stockport County
Full-time: Peterborough United 1-1 Stockport County
Referee: Charles Breakspear
Attendance: 11, 241 (1,473 Stockport County fans)