That looked like it could have been the winner but late goals from Tom Bradshaw and sub Matt Preston earned the Saddlers the 2-1 victory.
Alex Gilbey scored the only goal of the first half, heading home an Owen Garvan corner.
Two late goals have denied the U's a valuable win in heartbreaking style on Saturday.
Boss Kevin Keen made four changes to his starting line-up, bringing in Chris Porter, Gavin Massey, Nicky Shorey and Frankie Kent.
Tom Eastman, Matt Briggs, Macauley Bonne and Femi Akinwande were the quartet that missed out, with the latter two on the bench with Tom Lapslie, Richard Brindley, Darren Ambrose, Louis Dunne and keeper Dillon Barnes.
The game started with both sides wanting to get forward and it was the U’s who had the first shot, with Massey’s run ending with a shot wide of the target.
Elliot Lee then had a shot from the edge of the area blocked and Porter was denied by a low save as he headed goalwards from a U’s corner.
Sawyers did have a shot wide for the hosts but it was the U’s who would have been happier with the first ten minutes.
Alex Gilbey, who scored from distance last weekend, was given time and space to line up a shot but failed to test the home keeper from twenty five yards out.
Andy Taylor hit a free kick into the wall but his follow up shot was deflected wide for a corner, which came to nothing.
George Moncur was the next U’s player to try his luck from distance, but like the others, couldn’t find the target.
Lee then managed to get an attempt from closer in, but he was brilliantly tackled as he shot from ten yards out, with the keeper able to push it wide.
The corner was nervously punched out to Massey, but his volley was pushed away by the retreating Etheridge.
On the half hour mark, the hosts broke quickly, so quickly that Henry had to try his luck from a tight angle which Parish comfortably dealt with.
On thirty eight minutes, Owen Garvan won a superb challenge in midfield to release Moncur but his weak shot was straight into the hands of the home keeper.
With the first half in injury time, the U’s opened the scoring from a left wing corner.
Garvan’s set piece was perfect, as was Gilbey’s run and header and Etheridge could only get fingertips to it on its way into the bottom corner.
That was the last action of the half, with the referee’s whistle coming seconds after the hosts had restarted,
The expected reaction from the promotion chasing Saddlers never materialised at the start of the second half, with the U’s keeping them comfortably at bay.
So much so, the hosts didn’t have an effort at goal until the sixty fourth minute, with Henry shooting over from distance.
Before then, Massey was denied by Etheridge, who also had to be on his toes at his near post to snuff out some Elliot Lee danger.
The first time Parish was called into action was on seventy one minutes, when a Demetriou shot was hit straight at him.
Drey Wright was introduced two minutes later, with Lee going off, and then Darren Ambrose replaced George Moncur.
Joe Edwards, who had been outstanding at right back again, misjudged a diagonal ball and sub Lalkovic was in on the left.
The third and final change came on seventy eight minutes, with Macauley Bonne replacing Porter.
He couldn’t find an effective ball into the box though and Hiwula awkwardly skied his effort over the bar.
It was looking like the U’s were controlling things and were on their way to a rare win, with the hosts being kept at arm’s length.
That changed in the eighty eighth minute though, as Tom Bradshaw pounced when finally given a couple of yards of space.
Frankie Kent took his eye off the Saddlers’ top scorer for a second but it was enough for him to control and shoot past Parish to level things up.
That started a crazy few minutes to end the match, with the hosts now in the driving seat and looking for a winner.
It could have gone to the U’s as well though, as Ambrose headed wide from a delightful Garvan pass to the far post.
Bradshaw forced an excellent save from Parish deep into injury time, but the relief was shortlived as Walsall scored from the resultant corner.
The first effort hit the bar and Garvan on the line, but sub Matt Preston lashed the ball home to the delight of the home crowd, who had become increasingly frustrated as the game wore on.
It was a cruel finish to the game for the valiant U’s side, who in the past week had taken top teams to the wire but ended up with just one point from the two games against Wigan and Walsall.