Blue Square Bet Premier play-off chasers Darlington made it six games unbeaten in the league with a narrow victory over Cambridge.
Marc Bridge-Wilkinson, Ian Miller and Chris Senior squandered chances for the Quakers, who dominated throughout.
But they had to wait until the 67th minute for the breakthrough, Liam Hatch nodding home Senior's left-wing cross into the top corner from six yards.
Bridge-Wilkinson also hit the bar with a 74th-minute free-kick.
Cambridge United caretaker manager Jez George told BBC Radio Cambridgeshire: "They started really well, full of confidence. We got through that and, as the first half went on, we got more comfortable and had more possession.
"When you try to contain you have to take any gilt-edged chance, which we didn't.
"We let the lad get a run on us for the goal. He had a free header, guiding it into a dangerous area. They were quickest to react. That one moment's lapse of concentration cost us dearly."
Darlington: Russell, Arnison, Miller, Burn, Brown, Chandler, Verma, Gary Smith, Bridge-Wilkinson, Hatch, Michael Smith (Senior 59). Subs Not Used: St Louis-Hamilton, Quinn, McReady, Wright.
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