Peterborough blew a golden chance to clinch automatic promotion as they were stung by a fine comeback from Doncaster in a 2-2 deadlock.
Darren Ferguson's men needed victory against his former club to earn a rise into the Championship and all appeared to be going to plan as they took command in the first half.
Joe Ward provided the perfect start with a smart early strike before Sammie Szmodics slid in to double the advantage when converting Jack Taylor's cut-back in the 23rd minute.
That second goal was followed by a blast of fireworks as hundreds of fans gathered outside the stadium, but Doncaster soon put a dampener on the promotion party as Fejiri Okenabirhie struck from the edge of the box seven minutes before the break.
Ward was agonisingly denied further Posh goals by the crossbar on two occasions before Doncaster completed their fightback when substitute Taylor Richards tucked away Jason Lokilo's low cross in the 59th minute.
Neither side could strike again in a breathless second period.