Crewe manager Steve Davis admitted that the goalkeeping error by Chris Lewington was the turning point in his side's victory over Dagenham.
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.
"I couldn't see us breaking them down before the keeper made the error. We needed a moment of class or that bit of luck and we got it," said Davis. "I feel sorry for the lad but it helped us go on and win the game.
"When I came in we needed to get some wins on the board to restore the confidence. There's still work to do but we're getting there now and, if we keep winning, the league will look after itself.
"The play-offs are looking a realistic target now and the team is certainly good enough so we will keep trying to win games and let's see what happens."