In a dire first half, characterised by scrappy play, nasty tackles and sloppy passes, Kieron Freeman was a lone beacon of hope.
The full-back twice got forward well and on the second occasion profited from a rare piece of good passing to fire the ball across the area, with only a last-gasp David Gray clearance preventing a goal.
And it was Gray who eventually registered North End's first shot in the 54th minute as he ran onto a poor clearance and saw a deflected strike saved.
Allen had started only five of the players who did well against MK Dons on Saturday, and the dropped Lee Hughes came on to latch onto an excellent Neal Bishop through ball and sting the palms of Thorsten Stuckmann.
Alan Sheehan then saw his shot deflected inches wide and from the corner, Liam Chilvers' header was saved.
Hughes then crossed for substitute Ben Burgess, who out-jumped Stuckmann to head goalwards, but his effort was nodded off the line.
