Sporting Kansas City can watch the last round of fixtures in the MLS regular season at ease after winning the Eastern Conference on Wednesday.
Philadelphia remains in eighth place in the East.
Jack McInerney missed an excellent chance to give the Union the lead and score in his fifth consecutive game when his attempted chip of Jimmy Nielsen in the 35th minute went wide.
Jacob Petersen started the scoring in the 40th minute for Sporting, latching on to a low cross from Kei Kamara and touching the ball past Zac MacMath.
MacMath kept the Union in the game, his best contribution a fantastic double save right on the stroke of halftime.
The Union equalized in the second half. Michael Farfan's penalty was saved by Jimmy Nielsen, but Antoine Hoppenot was on hand to pounce and finish the rebound.
With less than 10 minutes left, SKC scored the winning goal. Kei Kamara wriggled through the entire Philly midfield on a long diagonal run. His measured through ball meant that all C.J. Sapong had to do was one-time a tidy near-post finish.
Kansas City's regular season is over, but the three points guarantee top spot in the East heading into the playoffs.
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