Over 1,000 Peterborough United fans made the journey to the Banks's Stadium and they will go away wondering how their side came away from nothing from league leaders Walsall.
Graham Westley's side created chances, were resilient at the back and if anyone looked like taking all three points, it would have been the Posh.
However, a goal on 80 minutes from full-back Demetriou took a wicked deflection off Miles Addison and wrong footed Ben Alnwick and from there on in, the hosts went on to secure the three points.
Addison was excellent at the back, but an injury to Michael Bostwick, one that could keep him out for two to three games, was a big blow.
The home side were inches away from opening the scoring inside the opening five minutes as Sam Mantom's low shot struck the post with goalkeeper Ben Alnwick left flat-footed.
Chris Forrester saw a 25-yard shot beaten away by Etheridge on eight minutes after a classy touch from Samuelsen in midfield.
The Saddlers were forced into a change on 12 minutes with Downing forced off the field, Matt Preston his replacement.
A poor pass from Forrester nearly sent Lalkovic clear on goal, but Smith made a good block before Alnwick denied Demetriou by his near post.
Bostwick produced an important block to deny Sawyers before Taylor fired over at the other end as the open nature of this clash continued.
Evans fired over on 32 minutes for the home side after a decent spell of pressure from the hosts.
A neat one two between Samuelsen and Smith ended with the latter firing well wide with his left-foot on 37 minutes.
On 41 minutes, Posh produced the move of the match as Maddison, Beautyman and Smith combined with the latter delivering a perfect cross on the run for Washington, who saw his header superbly tipped over by Etheridge.
A Bostwick cross caused all sorts of panic moments after the re-start, Angol's header at the back post eventually cleared.
On 49 minutes, a huge clearance from Alnwick was superbly taken down by Washington, but the in-form striker dragged his shot wide from a difficult angle.
Posh were forced into a change on the hour mark with Bostwick limping out of the action to be replaced by Almeida Santos.
A Maddison free-kick was diverted wide of the target by Addison moments later, a presentable heading opportunity wasted by the centre back.
Etheridge produced a fine fingertip save to tip a belter from Maddison over the bar on 64 minutes, the makeshift left-back letting fly from distance with his right-foot from 25-yards.
Mantom sent a curler from 20-yards wide of the target for the Saddlers on 69 minutes after cutting inside onto his left-foot.
Beautyman saw a shot blocked by Taylor before Angol fired the rebound over with his left-foot two minutes later.
Souleymane Coulibaly replaced Angol on 77 minutes. The hosts found the breakthrough on 80 minutes and they had that little bit of luck as DEMETRIOU saw his shot deflect off Addison and find the back of the net past Alnwick.
Westley made an immediate change with Erhun Oztumer replacing Beautyman. Washington was booked for a foul on the keeper moments later.
Alnwick produced a fine double stop to deny first Lalkovic and then Cook as Posh were caught on the counter attack.
The home side made the game safe on 88 minutes as EVANS fired low past Alnwick from close-range after a low cross into the box.
Five minutes of added time was indicated by the fourth official, but that second goal gave Posh no hope of getting back into the game.
Walsall: Etheridge, Demetriou, Taylor, O'Connor, Downing (sub Preston 12min), Chambers, Mantom (sub Forde 73min), Sawyers, Lalkovic, Cook (sub Morris 87min), Evans. Unused subs: Baxendale, Henry, Kinsella, Roberts.
Posh: Alnwick, Smith, Maddison, Bostwick (sub Almeida Santos 60min), Addison, Forrester, Taylor, Beautyman (sub Oztumer 80min), Samuelsen, Angol (sub Coulibaly 77min), Washington. Unused subs: Henry, Baldwin, Fox, Nicholson.
Half-time: Walsall 0-0 Peterborough United
Full-time: Walsall 2-0 Peterborough United
Attendance: 6,142 (1,045 Posh fans)