It was another tactical success for Walsall player-manager Paul Merson, who again left himself out of the side and opted to pack five men into midfield. The ploy worked at Swindon the previous weekend and was just as effective in what was really a must-win game for Posh.
But, after having the better of the of first half chances, with Steve Thomson firing inches too high within a couple of minutes of Callum Willock rattling the Walsall crossbar, Barry Fry's side were twice opened up in the second half.
The warning signs were there when Mark Wright missed a good chance for Walsall five minutes before the break, firing into the side netting after being set-up by Darren Wrack. Then Julian Joachim saw a fierce shot deflected behind by Chris Plummer during added time.
It was an initiative Walsall retained into the second half and they first rocked Posh with a swift counter attack on 66 minutes. Peterborough born Joachim, on loan from Leeds United, raced free to slot a pass into the path of Michael Standing and the 24 year-old midfield man netted with a right footed shot form the edge of the penalty area.
With their strong numerical presence in the middle of the field Walsall were able to soak up Posh pressure as Fry rang the changes and committed three strikers.
The Saddlers made the points safe when extending their lead with Wrack picking up a loose ball and giving home goalkeeper Mark Tyler no chance with a decisive 78th minute strike.