Dagenham coach Terry Harris says Chris Lewington's goalkeeping error cost his side dearly as Crewe walked away with a 4-1 win.
Lewington's air shot allowed Abu Agogo's backpass to cross the line and put the Alex in front after Greg Pearson had cancelled out Brian Woodall's 16th-minute opener.
Adam Dugdale and Nick Powell then both netted in the last 10 minutes to stick the knife in as the Daggers collapsed.
Harris said: "The mistake has cost us but these things happen. Chris looks like he has gone to leather it and he's missed it. Maybe he should have taken another touch first but he's a young lad and he will learn from it.
"The ball had gone out for their third goal but the linesman missed it and then they score and we collapse.
"But we're staying positive. We gave a good account of ourselves and their keeper had more saves to make than ours did so we just need to put this behind us and move onto the next game."