He smacked in a shot on 20 minutes that was always going wide, before sending in another that Walker was happy to claim close to his chest.
Jon Taylor was the man who was causing most of the problems for the Shrews, drifting in off the wing to cause problems on the edge of the box.
It was to perhaps sum up both teams' first half efforts in the game, where things went well until things reached the final third.
It was on eleven minutes that the U's first saw goal as a clever interchange down the right hand side got Porter into the box and he cut it back to Sears who came onto it at such pace, he was unable to get a clean connection on his shot.
The match, watched by just under 6,000 people, saw an even start from both sides, as they looked to settle into a routine for the rest of the match.
It narrowed the gap to three points, and so all attentions will turn to that trip at Brunton Park where the U's know they have to get at least a point in the north to assure their safety.
They never truly got into top gear in a nervous display in front of their own supporters and know that they now have to go to Carlisle to ensure their status in the division, after Scunthorpe United grabbed a win at MK Dons.
The U's quest for League One safety will go to the final day of the season, after they were unable to find a way to break down Shrewsbury Town in front of their best crowd of the season.
McGinn had a similar chance that he put wide, before Ibehre had a shot after a clever ball into the box by White that Weale was able to collect at his near post.
The U's fortunes in the first half were summed up when some good wing play from Porter in the last ten minutes of the half saw the ball fall at the feet of Clifford, but his placed shot, destined to test Weale low to his left, caught Massey and went away to safety.
The visitors were dangerous on the break and McAllister fired wide from the edge of the area after being set up by Bradshaw.
That point could prove to be crucial in next week's reckonings, but the U's will be frustrated they didn't complete the job in front of their own fans.
Twice he managed to get past the U's man but last ditch U's defending got the ball away and preserved the clean sheet.
In fact, Shrewsbury were probably finishing the stronger, taking the U's on the counter attack with Taylor the chief threat as he had a running battle with Wilson.
The U's pressed their opponents but were unable to find a way through to Weale and the clock was starting to run down on the U's hopes of finding a home winner.
McAllister went close next up on the hour mark, having been allowed to run to the edge of the box before forcing a fine full length save out of Walker.
Porter's throws were causing problems in the Shrewsbury defence, but they protected their keeper well, although it needed swift action when one fell into the six yard area for something of a goalmouth scramble.
In the second half, the U's saw Sears half volley one into the arms of Weale, before Ibehre headed straight at the keeper from a cross on the right.