After Drew Talbot was sent off in the first half, the U's laid siege to the Chesterfield goal and had a multitude of chances as they sought their first win of the season.
But, having hit the woodwork three times and forced Tommy Lee in the Spireites goal into a range of excellent saves, the U's found themselves 3-1 down with just under twenty minutes to play.
Lesser sides may have folded at that point and accepted defeat, but this side has character and fought back late on in the game to seal another point.
The U's made three changes to their starting eleven from the last league game against Scunthorpe United.
Jamie Jones came in to replace Elliott Parish in goal, Owen Garvan was chosen ahead of George Moncur and Marvin Sordell was the man given the responsibility of leading the line, with Macauley Bonne dropping to the bench.
The visitors had the first sight of goal as, after the ball from a U's corner was cleared, Briggs returned the ball with a low shot that Lee saved well.
The home side then had a chance of their own, as Ariyibi broke the offside trap but, from a tight angle, Jones was able to comfortably field the shot.
Debutant Sordell looked like he was about to grab his first U's goal within the first ten minutes when some good interchange on the edge of the box put him in.
He was about to pull the trigger before Talbot appeared at the last moment to take the ball away from the U's number 45.
The U's had a golden chance to take the lead on fourteen minutes when Harriott, with three assists in his first two games, slid in Gilbey. The midfielder steadied himself and hit a low shot that Lee pulled out a top drawer save to deny the U’s man.
The home side were then reduced to ten men after 15 minutes as Sordell broke the offside trap and tangled legs with the retreating defender.
From the resulting free kick, Garvan stepped up, but curled it over the bar with Lee scrambling across his goal.
Despite the U's being well on top, they were nearly behind on nineteen minutes. A long ball over the top found Novak and his lobbed effort beat Jones, but also went over the crossbar.
Sordell was proving to be a real nuisance. He again broke the offside trap midway through the first half, but couldn’t get the ball out of his feet. He slid in Harriott and although he scored, he was flagged offside well before that.
The U's then fell behind midway through the first half. The ball was swung in from a free kick by Jones and it went all the way in and dropped in at the far post.
The U's reacted quickly, making their first change on 28 minutes. George Moncur replaced Joe Edwards as they went even more on the attack.
And the change paid dividends two minutes later. Harriott’s low centre just missed Moncur, but it found Massey who calmly sidefooted home.
Moncur then had a chance of his own as Massey cut one back to him inside the box, but he didn't quite hit his shot cleanly and it went wide of the post.
Five minutes before half time, the U’s had another great chance. Moncur set Sordell away, he rounded Lee and took it well wide of goal.
With no angle to shoot, he cut it back to Harriott and it was a fine block by Raglan as it went over the bar.
The Charlton loanee went even closer two minutes before the interval. A long passing move ended with Harriott springing the offside trap and his shot hit the inside of the post and somehow stayed out.
The U's had pressed for the whole of the first half and should have been in front twice within the first ten minutes of the second half.
First, Gilbey crashed one against the top of the post, before some Moncur magic ended with Massey's low cross being missed from close range by Sordell.
The U's next chance came through the impressive Garvan who decided to shoot not pass this time, and it was well saved by Lee with Sordell lingering with intent.
All of that U's pressure counted for nothing though when they found themselves behind again. The ball was long at the back post, but it was cut back for Novak to slot home from close range.
The U's nearly drew level within minutes. The ball was crossed into the danger area, Sordell met it with a fine header, from which Lee pulled off another brilliant save.
The visitors missed chances came back to haunt them further with fifteen minutes to go as the ball found Morsy on the far post and he volleyed home to extend the home side's advantage.
That two goal advantage didn't last long though as Garvan set the ball out to Harriott and his low cross found Moncur to smash home.
Garvan then went close again, lashing in a shot that took a deflection as it went inches wide. At the other end, Harrison was denied by a good save as the U's were hit on the counter attack.
The visitors then went close again as Massey cut the ball back to Gilbey, but he spurned a great chance from eight yards out.
They did get level in injury time, though. Moncur sprung the offside trap, missed the first chance to shoot but then hit the bar. The ball was put back into the danger area and it eventually went in off Raglan to send the visiting fans crazy.
The U's will be left wondering how they didn't win the game, but they will be consoled by their fighting spirit to get something out of the match.