Cambridge grabbed a well-earned replay after a 0-0 draw against League One high-flyers Huddersfield at the Abbey Stadium.
At times the visitors, 61 places higher than the hosts in the league ladder, were sloppy and they could not break down the resilient Blue Square Bet Premier side.
Chances were at a premium throughout the game but the hosts would not have minded as they frustrated the free-scoring visitors, the best chances coming in the second-half for both sides.
Huddersfield winger Anthony Pilkington forced Cambridge stopper Danny Naisbitt into a low save before fizzing a long-range drive past the post.
United's Danny Wright who had the best chance of the game when he got on the end of Wayne Gray's low cross only to turn the ball straight at Town keeper Ian Bennett.
Benik Afobe, on loan from Arsenal, showed glimpses of his undoubted potential, forcing Naisbitt into a full stretch save with time running out but the U's could have nicked it in time added on.
But Simon Russell could not get a shot off before Cambridge winger Robbie Willmott shot straight at Bennett.
Cambridge also had a late penalty shout but in the end the draw was always on the cards.