Philadelphia (11-10-9) moved into the fifth and final playoff position in the Eastern Conference, one point behind Houston and two in front of New England.
The Philadelphia goal came after Danny Cruz sent a cross into the box that Michael Farfan directed toward the net. Jimmy Nielsen was able to stop the shot, but Casey put home the rebound for his 11th goal of the campaign.
Sporting KC (14-10-6) remained in second place in the East, missing out on a chance to move into a first-place tie with New York.
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