The U's are out of the Johnstone's Paint Trophy.
A second half comeback from Dagenham & Redbridge saw them run out comfortable 4-1 winners.
Brian Wilson gave the U's a 1-0 half but the hosts turned things round after the break.
They had already equalised when Magnus Okuonghae was sent off and then ran in three further goals.
The bad news didn't finish there though, injuries to Gavin Massey and Clinton Morrison saw them replaced and Okuonghae now faces a one game suspension.
Joe Dunne made four changes to the U’s starting eleven, bringing in Brian Wilson, Andy Bond, Alex Gilbey and Clinton Morrison.
David Wright, Sanchez Watt, Freddie Sears and Jabo Ibehre made way, with Wright and Ibehre making the bench.
It was the U’s who started the better, with the first ten minutes seeing a few crosses put low into the daggers’ box, without a final touch being applied.
The only time Seabright in the home goal was tested though, was when Andy Bond shot straight at him from the edge of the box.
The next effort on goal came again from the visitors, as a strong run by Alex Gilbey ended with the young midfielder shooting well wide.
Halfway through the first period, Magnus Okuonghae was booked for a foul but the free kick was wasted by Zavon Hines.
Hines was then off target again on the half hour mark, volleying well wide after Tom Eastman headed a cross to the edge of the penalty area.
A low cross then evaded Eastman but Obafemi failed to capitalise, being caught on his heels.
With eight minutes to go until the break, Tosin Olufemi was upended by Doe, who received a yellow card but was to be punished further from the resultant set piece.
New U’s club captain Brian Wilson stepped up and curled a lovely free kick into the far corner, putting the U’s into the lead.
Sam Walker had been a virtual spectator in the first forty five minutes, and it took the Daggers until injury time to get a shot on target.
Obafemi had got himself a bit of space twenty yards out but his shot lacked any pace and Walker made a regulation save down to his right.
The U’s had looked assured and in control in the first half and Dunne would have been asking for more of the same in the second forty five minutes.
Home boss Wayne Burnett wouldn’t have been as happy though, and whatever was said during the break in the Daggers’ dressing room had an immediate effect.
Former U’s starlet Medy Elito manufactured the first opportunity but his shot ended up just wide of Walker’s upright.
That chance came on forty eight minutes and less than five minutes later, Elito put his side level with a great header.
Good build-up play down the right ended with a deep cross to the far post and Elito easily outjumped Jabo Ibehre to power home his header.
Ibehre tried to make amends straight away, having two efforts saved within three minutes of the Daggers’ leveller.
Just after the hour, the pivotal minute of the game arrived, with the dismissal of Okuonghae and the second Dagenham goal.
Hines was having a massively improved second half and he twisted inside and out before being tripped by Okuonghae.
There weren’t too many arguments about the second yellow, although the first yellow in the first half for the U’s defender could have been deemed a little harsh.
The U’s wanted to bring Josh Thompson on straight away but they had to wait until the resultant free kick had been taken.
The set piece proved costly, as Hines got free on the left and crossed low for Saah to tap in from close range.
It was all Dagenham at this stage and captain Ogogo got in on the act to make it 3-1 before Hines set up sub Dennis in the eighty sixth minute to complete the scoring.
For the fifth year in succession, the U’s were out of the Johnstone’s Paints Trophy but there were also injuries to Gavin Massey and Clinton Morrison that compounded the agony.