The U's have lost 1-0 at Coventry City as the Sky Blues edged away from the relegation battle.
Coventry skipper Jim O'Brien opened the scoring after thirty five minutes, latching onto a pull back from Chris Stokes.
Despite a spirited second half from the U's, a leveller never came and the hosts took the three points.
The defeat meant the gap to safely for the U's increased from two to three points, with five games remaining.
Boss Tony Humes made one change to his starting line-up, bringing back Alex Gilbey into midfield, with Sammie Szmodics dropping down to the bench.
In the early stages, both sides were feeling their way into things, with neither Sam Walker nor home keeper Lee Burge unduly tested.
In fact, it was twelve minutes before either had a meaningful touch, Walker collecting easily from Jim O’Brien’s header.
Burge had his own comfortable save a minute later, as he safely held Gavin Massey’s low shot.
A shot from distance by Barton then flew wide before Walker had to be alert to save as Proschwitz got on the end of Tom Eastman’s back header.
The home side was having the better of the possession but Walker wasn’t called into action for the next trio of efforts, all finishing well wide of his goal.
It was a different story on thirty five minutes though, as Coventry opened the scoring through their captain O’Brien.
The U’s didn’t clear an attack and left back Chris Stokes evaded a rash challenge by Richard Brindley before pulling it back for O’Brien to sidefoot home.
Confidence flowed through the home side in the remainder of the half and the U’s found it difficult to get any decent possession of the ball.
Fortunately, Coventry didn’t get through the U’s back four though and the half time whistle went with the score 1-0 to the hosts.
As with the previous four matches, a better second half was required, and the U’s players were on the attack from the off.
Within two minutes, George Moncur cut inside onto his left foot and was only denied by a diving save from Burge.
The U’s midfielder will feel that he should have maybe found the back of the net but his effort allowed the keeper to make the important save.
A minute later and Moncur turned provider, setting up Gavin Massey on the left who was denied by an even better save from Burge.
The U’s were pushing men forward looking for an equaliser and the gaps left gave the hosts an opportunity on fifty five minutes.
Proschwitz latched onto a through ball, rounded Walker but with the goal gaping found the sidenetting when it was perhaps easier to find the net.
It was a let off for the U’s, but it didn’t upset their forward momentum and Moncur was at the heart of everything good.
He wriggled free on the right of the six yard box but was denied by a last ditch block by a couple of defenders.
The resulting corner found the head of Chris Porter but his header was straight at Burge, who was by far the busier of the two keepers in the second half.
On sixty seven minutes, Lapslie and Wynter were replaced by Briggs and Szmodics, and a few minutes later, Porter went off for Rhys Healey.
Richard Brindley had the next effort for the U’s, driving forward before hitting a shot past the post.
With ten minutes remaining, Walker tipped a Maddison effort onto the post and the U’s hit the woodwork themselves three minutes later.
Tom Eastman headed the ball down to Szmodics and with his back to goal, the youngster hooked the ball over his shoulder but it bounced off the top of the bar to safety.
That was the final chance for the U’s to get back in the game and the referee blew the whistle after five minutes of added time.
Before the game, the gap to safety was two points – that increased to three following this defeat, putting pressure on the U’s to get a positive result on Tuesday at Chesterfield.