The home side had the first shot of the game when a ball forward down the right found Gavin Massey, but the former Watford man could only drag his shot wide of the post from a tight angle.
Colchester's Elliot Parish was the first goalkeeper to be called into action when Jonathan Forte's shot required a strong hand to tip it away at the near post, before Liam Kelly tested him with a curling effort from outside the box.
United started the second period well, with Joe Edwards volleying over from 20 yards and Darren Ambrose shooting wide from the edge of the box, before Sammie Szmodics's sliding effort came back off the post with Joel Coleman beaten.
However, it could have been the Latics who took the lead were it not for a double save from Parish, first from Forte's effort and then secondly to deny Croft.
Croft had another opportunity when he could not bundle home Forte's centre late on, but there was nothing to separate the sides at the final whistle.
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