OXFORD United suffered the cruellest of defeats as a freak own goal in the dying minutes handed Dagenham & Redbridge a fortuitous victory.
A tight game looked destined to finish goalless, but a minute from the end of normal time, the visitors were hit by a hammer blow.
Luke Howell's shot was blocked by Michael Raynes and the ball ricocheted off Matt Bevans' knees, looping over goalkeeper Ryan Clarke into the net.
It was harsh on a hard-working United side who were not at their best but deserved at least a point.
They had chances to take all three, as Ryan Williams fired off target at the end of a slick move in the first half and James Constable had two sights of goal after coming on as a substitute.
But it was not to be, as United slipped to a fourth successive away defeat and the level of frustration was demonstrated by a brief altercation between skipper Jake Wright and a handful of supporters as the players headed for the changing room.
Gary Waddock made four changes to the side which were well beaten at Southend United on Monday.
Raynes came in for Sam Long at centre half, Scott Davies and Andy Whing replaced Danny Rose and Sean Rigg in midfield, while up front David Connolly was preferred to James Constable.
A fifth alteration was needed before kick-off. Alfie Potter picked up an injury in the warm-up, so Williams was promoted from the bench at short notice.
United had lost their previous three away games 3-0 and they did not start promisingly.
Just three minutes were on the clock when a loose pass from Jake Wright was intercepted by Ashley Chambers, but fortunately the ball ran to goalkeeper Ryan Clarke.
Dagenham, unbeaten in their last seven games, took advantage of their stuttering visitors and made all the early running.
A deep cross from the right on nine minutes found Medy Elito in space at the back post, but the winger sliced a good opportunity wide.
Wright, who had struggled at Roots Hall, made another mistake midway through the half. Chambers caught the U's skipper in possession and burst into the box, where Raynes had to make a hurried clearance.
United were below par and sloppy in possession, but perhaps inspired by a loud travelling following they gradually got their act together.
It took almost half an hour to pose any kind of threat, when Connolly, who had been starved of service, had a shot blocked after Raynes flicked on David Hunt's long throw.
Williams was not supposed to be on the pitch, but the winger suddenly came to life.
A flash of skill nine minutes before the break saw him beat Jack Connors and play in Josh Ruffels. The Australian kept running and was on hand to receive the cut-back, but blasted off target from 15 yards.
It began a bright spell for United up to half-time, as they kept the ball well and pinned Dagenham back.
Williams provided the spark again late in the half, playing Davies into the area, where he found Ruffels to fire a shot, which was deflected wide.
It gave United plenty of encouragement heading into the break, but it disrupted their rhythm.
Instead, Dagenham reasserted themselves and should have taken the lead 11 minutes after the restart.
A low cross from the left found Luke Norris, who smartly spun into space before blasting over from ten yards.
It was a glorious chance in the context of a tight game and the striker's frustrated reaction suggested he knew it.
United struggled to impose themselves and Waddock had to turn to the bench for inspiration.
Rigg, Constable and Nicky Wroe all came on in quick succession in the hope of giving the visitors fresh impetus.
A chance duly arrived, with Raynes leaping to head wide from Hunt's throw.
Constable also quickly had a chance, collecting a cross and firing a shot on the turn which Chris Lewington blocked with his legs.
The game began to open up as both sides looked for a winner in the final ten minutes.
Dagenham opened United up four minutes from time, but a brilliant challenge from Whing denied substitute Chris Dickson a tap-in.
But the visitors were hit with a hammer blow a minute from the end of normal time.
The goal came in bizarre fashion as a clearance struck Raynes and Bevans on the edge of the box before looping over Clarke into the net.
Constable had a sight of goal in stoppage time, but after teeing himself up the striker shot wide.
Oxford Utd: Clarke, Bevans, Raynes, Wright, Hunt, Davies, Whing, Ruffels, Williams (Wroe 74), Smalley (Rigg 68), Connolly (Constable 72).
Unused subs: Crocombe, Long, Rose, Potter.
Dagenham: Lewington, Hoyte, Doe, Saah, Connors, Ogogo, Chambers, Howell, Turgott (Azeez 69), Norris (Dickson 81), Elito.
Unused subs: Seabright, Bingham, D'Ath, Shields, Gayle.
Referee: Trevor Kettle (Rutland).
Attendance: 1,893 (598 visitors).