After a 30 minute delay of kickoff, the teams with the best records in the Eastern Conference squared off, with the Crew coming out on top.
Both home goals were created by Robbie Rogers. The U.S. international crossed from the left and Emilio Renteria bounced it in to open net the scoring in the 37th minute.
In the second half, a Rogers cross struck the hand of Sheanon Williams in the box. Mendoza denied Rogers the chance to take the penalty and the DP's penalty squirted under Faryd Mondragon to decide the match.
Between those two goals, the Union had tied it up briefly, with Veljko Paunovic heading home a Keon Daniel corner at the close of the first half.
The result, the Crew's fourth win in five games, takes Columbus six points clear in the East, though Philly has a game in hand.